sgi-xp: isolate additional sn2 specific code

[linux-2.6] / drivers / misc / sgi-xp / xpc_sn2.c

/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (c) 2008 Silicon Graphics, Inc.  All Rights Reserved.
 */

/*
 * Cross Partition Communication (XPC) sn2-based functions.
 *
 *     Architecture specific implementation of common functions.
 *
 */

#include <linux/kernel.h>
#include <linux/delay.h>
#include <asm/uncached.h>
#include <asm/sn/sn_sal.h>
#include "xpc.h"

static struct xpc_vars_sn2 *xpc_vars;   /* >>> Add _sn2 suffix? */
static struct xpc_vars_part_sn2 *xpc_vars_part; /* >>> Add _sn2 suffix? */

/* SH_IPI_ACCESS shub register value on startup */
static u64 xpc_sh1_IPI_access;
static u64 xpc_sh2_IPI_access0;
static u64 xpc_sh2_IPI_access1;
static u64 xpc_sh2_IPI_access2;
static u64 xpc_sh2_IPI_access3;

/*
 * Change protections to allow IPI operations.
 */
static void
xpc_allow_IPI_ops_sn2(void)
{
        int node;
        int nasid;

        /* >>> The following should get moved into SAL. */
        if (is_shub2()) {
                xpc_sh2_IPI_access0 =
                    (u64)HUB_L((u64 *)LOCAL_MMR_ADDR(SH2_IPI_ACCESS0));
                xpc_sh2_IPI_access1 =
                    (u64)HUB_L((u64 *)LOCAL_MMR_ADDR(SH2_IPI_ACCESS1));
                xpc_sh2_IPI_access2 =
                    (u64)HUB_L((u64 *)LOCAL_MMR_ADDR(SH2_IPI_ACCESS2));
                xpc_sh2_IPI_access3 =
                    (u64)HUB_L((u64 *)LOCAL_MMR_ADDR(SH2_IPI_ACCESS3));

                for_each_online_node(node) {
                        nasid = cnodeid_to_nasid(node);
                        HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS0),
                              -1UL);
                        HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS1),
                              -1UL);
                        HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS2),
                              -1UL);
                        HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS3),
                              -1UL);
                }
        } else {
                xpc_sh1_IPI_access =
                    (u64)HUB_L((u64 *)LOCAL_MMR_ADDR(SH1_IPI_ACCESS));

                for_each_online_node(node) {
                        nasid = cnodeid_to_nasid(node);
                        HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH1_IPI_ACCESS),
                              -1UL);
                }
        }
}

/*
 * Restrict protections to disallow IPI operations.
 */
static void
xpc_disallow_IPI_ops_sn2(void)
{
        int node;
        int nasid;

        /* >>> The following should get moved into SAL. */
        if (is_shub2()) {
                for_each_online_node(node) {
                        nasid = cnodeid_to_nasid(node);
                        HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS0),
                              xpc_sh2_IPI_access0);
                        HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS1),
                              xpc_sh2_IPI_access1);
                        HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS2),
                              xpc_sh2_IPI_access2);
                        HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS3),
                              xpc_sh2_IPI_access3);
                }
        } else {
                for_each_online_node(node) {
                        nasid = cnodeid_to_nasid(node);
                        HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH1_IPI_ACCESS),
                              xpc_sh1_IPI_access);
                }
        }
}

/*
 * The following set of macros and functions are used for the sending and
 * receiving of IPIs (also known as IRQs). There are two flavors of IPIs,
 * one that is associated with partition activity (SGI_XPC_ACTIVATE) and
 * the other that is associated with channel activity (SGI_XPC_NOTIFY).
 */

static u64
xpc_IPI_receive_sn2(AMO_t *amo)
{
        return FETCHOP_LOAD_OP(TO_AMO((u64)&amo->variable), FETCHOP_CLEAR);
}

static enum xp_retval
xpc_IPI_send_sn2(AMO_t *amo, u64 flag, int nasid, int phys_cpuid, int vector)
{
        int ret = 0;
        unsigned long irq_flags;

        local_irq_save(irq_flags);

        FETCHOP_STORE_OP(TO_AMO((u64)&amo->variable), FETCHOP_OR, flag);
        sn_send_IPI_phys(nasid, phys_cpuid, vector, 0);

        /*
         * We must always use the nofault function regardless of whether we
         * are on a Shub 1.1 system or a Shub 1.2 slice 0xc processor. If we
         * didn't, we'd never know that the other partition is down and would
         * keep sending IPIs and AMOs to it until the heartbeat times out.
         */
        ret = xp_nofault_PIOR((u64 *)GLOBAL_MMR_ADDR(NASID_GET(&amo->variable),
                                                     xp_nofault_PIOR_target));

        local_irq_restore(irq_flags);

        return ((ret == 0) ? xpSuccess : xpPioReadError);
}

static AMO_t *
xpc_IPI_init_sn2(int index)
{
        AMO_t *amo = xpc_vars->amos_page + index;

        (void)xpc_IPI_receive_sn2(amo); /* clear AMO variable */
        return amo;
}

/*
 * IPIs associated with SGI_XPC_ACTIVATE IRQ.
 */

/*
 * Notify the heartbeat check thread that an activate IRQ has been received.
 */
static irqreturn_t
xpc_handle_activate_IRQ_sn2(int irq, void *dev_id)
{
        atomic_inc(&xpc_activate_IRQ_rcvd);
        wake_up_interruptible(&xpc_activate_IRQ_wq);
        return IRQ_HANDLED;
}

/*
 * Flag the appropriate AMO variable and send an IPI to the specified node.
 */
static void
xpc_activate_IRQ_send_sn2(u64 amos_page_pa, int from_nasid, int to_nasid,
                      int to_phys_cpuid)
{
        int w_index = XPC_NASID_W_INDEX(from_nasid);
        int b_index = XPC_NASID_B_INDEX(from_nasid);
        AMO_t *amos = (AMO_t *)__va(amos_page_pa +
                                    (XPC_ACTIVATE_IRQ_AMOS * sizeof(AMO_t)));

        (void)xpc_IPI_send_sn2(&amos[w_index], (1UL << b_index), to_nasid,
                               to_phys_cpuid, SGI_XPC_ACTIVATE);
}

static void
xpc_activate_IRQ_send_local_sn2(int from_nasid)
{
        int w_index = XPC_NASID_W_INDEX(from_nasid);
        int b_index = XPC_NASID_B_INDEX(from_nasid);
        AMO_t *amos = (AMO_t *)__va(xpc_vars->amos_page_pa +
                                    (XPC_ACTIVATE_IRQ_AMOS * sizeof(AMO_t)));

        /* fake the sending and receipt of an activate IRQ from remote nasid */
        FETCHOP_STORE_OP(TO_AMO((u64)&amos[w_index].variable), FETCHOP_OR,
                         (1UL << b_index));
        atomic_inc(&xpc_activate_IRQ_rcvd);
        wake_up_interruptible(&xpc_activate_IRQ_wq);
}

/*
 * IPIs associated with SGI_XPC_NOTIFY IRQ.
 */

/*
 * Check to see if there is any channel activity to/from the specified
 * partition.
 */
static void
xpc_check_for_channel_activity_sn2(struct xpc_partition *part)
{
        u64 IPI_amo;
        unsigned long irq_flags;

        IPI_amo = xpc_IPI_receive_sn2(part->sn.sn2.local_IPI_amo_va);
        if (IPI_amo == 0)
                return;

        spin_lock_irqsave(&part->IPI_lock, irq_flags);
        part->local_IPI_amo |= IPI_amo;
        spin_unlock_irqrestore(&part->IPI_lock, irq_flags);

        dev_dbg(xpc_chan, "received IPI from partid=%d, IPI_amo=0x%lx\n",
                XPC_PARTID(part), IPI_amo);

        xpc_wakeup_channel_mgr(part);
}

/*
 * Handle the receipt of a SGI_XPC_NOTIFY IRQ by seeing whether the specified
 * partition actually sent it. Since SGI_XPC_NOTIFY IRQs may be shared by more
 * than one partition, we use an AMO_t structure per partition to indicate
 * whether a partition has sent an IPI or not.  If it has, then wake up the
 * associated kthread to handle it.
 *
 * All SGI_XPC_NOTIFY IRQs received by XPC are the result of IPIs sent by XPC
 * running on other partitions.
 *
 * Noteworthy Arguments:
 *
 *      irq - Interrupt ReQuest number. NOT USED.
 *
 *      dev_id - partid of IPI's potential sender.
 */
static irqreturn_t
xpc_handle_notify_IRQ_sn2(int irq, void *dev_id)
{
        short partid = (short)(u64)dev_id;
        struct xpc_partition *part = &xpc_partitions[partid];

        DBUG_ON(partid < 0 || partid >= xp_max_npartitions);

        if (xpc_part_ref(part)) {
                xpc_check_for_channel_activity_sn2(part);

                xpc_part_deref(part);
        }
        return IRQ_HANDLED;
}

/*
 * Check to see if xpc_handle_notify_IRQ_sn2() dropped any IPIs on the floor
 * because the write to their associated IPI amo completed after the IRQ/IPI
 * was received.
 */
static void
xpc_dropped_notify_IRQ_check_sn2(struct xpc_partition *part)
{
        struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;

        if (xpc_part_ref(part)) {
                xpc_check_for_channel_activity_sn2(part);

                part_sn2->dropped_notify_IRQ_timer.expires = jiffies +
                    XPC_P_DROPPED_IPI_WAIT_INTERVAL;
                add_timer(&part_sn2->dropped_notify_IRQ_timer);
                xpc_part_deref(part);
        }
}

/*
 * Send an IPI to the remote partition that is associated with the
 * specified channel.
 */
static void
xpc_notify_IRQ_send_sn2(struct xpc_channel *ch, u8 ipi_flag,
                        char *ipi_flag_string, unsigned long *irq_flags)
{
        struct xpc_partition *part = &xpc_partitions[ch->partid];
        struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;
        enum xp_retval ret;

        if (likely(part->act_state != XPC_P_DEACTIVATING)) {
                ret = xpc_IPI_send_sn2(part_sn2->remote_IPI_amo_va,
                                       (u64)ipi_flag << (ch->number * 8),
                                       part_sn2->remote_IPI_nasid,
                                       part_sn2->remote_IPI_phys_cpuid,
                                       SGI_XPC_NOTIFY);
                dev_dbg(xpc_chan, "%s sent to partid=%d, channel=%d, ret=%d\n",
                        ipi_flag_string, ch->partid, ch->number, ret);
                if (unlikely(ret != xpSuccess)) {
                        if (irq_flags != NULL)
                                spin_unlock_irqrestore(&ch->lock, *irq_flags);
                        XPC_DEACTIVATE_PARTITION(part, ret);
                        if (irq_flags != NULL)
                                spin_lock_irqsave(&ch->lock, *irq_flags);
                }
        }
}

#define XPC_NOTIFY_IRQ_SEND_SN2(_ch, _ipi_f, _irq_f) \
                xpc_notify_IRQ_send_sn2(_ch, _ipi_f, #_ipi_f, _irq_f)

/*
 * Make it look like the remote partition, which is associated with the
 * specified channel, sent us an IPI. This faked IPI will be handled
 * by xpc_dropped_notify_IRQ_check_sn2().
 */
static void
xpc_notify_IRQ_send_local_sn2(struct xpc_channel *ch, u8 ipi_flag,
                              char *ipi_flag_string)
{
        struct xpc_partition *part = &xpc_partitions[ch->partid];

        FETCHOP_STORE_OP(TO_AMO((u64)&part->sn.sn2.local_IPI_amo_va->variable),
                         FETCHOP_OR, ((u64)ipi_flag << (ch->number * 8)));
        dev_dbg(xpc_chan, "%s sent local from partid=%d, channel=%d\n",
                ipi_flag_string, ch->partid, ch->number);
}

#define XPC_NOTIFY_IRQ_SEND_LOCAL_SN2(_ch, _ipi_f) \
                xpc_notify_IRQ_send_local_sn2(_ch, _ipi_f, #_ipi_f)

static void
xpc_send_channel_closerequest_sn2(struct xpc_channel *ch,
                                  unsigned long *irq_flags)
{
        struct xpc_openclose_args *args = ch->local_openclose_args;

        args->reason = ch->reason;
        XPC_NOTIFY_IRQ_SEND_SN2(ch, XPC_IPI_CLOSEREQUEST, irq_flags);
}

static void
xpc_send_channel_closereply_sn2(struct xpc_channel *ch,
                                unsigned long *irq_flags)
{
        XPC_NOTIFY_IRQ_SEND_SN2(ch, XPC_IPI_CLOSEREPLY, irq_flags);
}

static void
xpc_send_channel_openrequest_sn2(struct xpc_channel *ch,
                                 unsigned long *irq_flags)
{
        struct xpc_openclose_args *args = ch->local_openclose_args;

        args->msg_size = ch->msg_size;
        args->local_nentries = ch->local_nentries;
        XPC_NOTIFY_IRQ_SEND_SN2(ch, XPC_IPI_OPENREQUEST, irq_flags);
}

static void
xpc_send_channel_openreply_sn2(struct xpc_channel *ch, unsigned long *irq_flags)
{
        struct xpc_openclose_args *args = ch->local_openclose_args;

        args->remote_nentries = ch->remote_nentries;
        args->local_nentries = ch->local_nentries;
        args->local_msgqueue_pa = __pa(ch->local_msgqueue);
        XPC_NOTIFY_IRQ_SEND_SN2(ch, XPC_IPI_OPENREPLY, irq_flags);
}

static void
xpc_send_channel_msgrequest_sn2(struct xpc_channel *ch)
{
        XPC_NOTIFY_IRQ_SEND_SN2(ch, XPC_IPI_MSGREQUEST, NULL);
}

static void
xpc_send_channel_local_msgrequest_sn2(struct xpc_channel *ch)
{
        XPC_NOTIFY_IRQ_SEND_LOCAL_SN2(ch, XPC_IPI_MSGREQUEST);
}

/*
 * This next set of functions are used to keep track of when a partition is
 * potentially engaged in accessing memory belonging to another partition.
 */

static void
xpc_indicate_partition_engaged_sn2(struct xpc_partition *part)
{
        unsigned long irq_flags;
        AMO_t *amo = (AMO_t *)__va(part->sn.sn2.remote_amos_page_pa +
                                   (XPC_ENGAGED_PARTITIONS_AMO *
                                    sizeof(AMO_t)));

        local_irq_save(irq_flags);

        /* set bit corresponding to our partid in remote partition's AMO */
        FETCHOP_STORE_OP(TO_AMO((u64)&amo->variable), FETCHOP_OR,
                         (1UL << sn_partition_id));
        /*
         * We must always use the nofault function regardless of whether we
         * are on a Shub 1.1 system or a Shub 1.2 slice 0xc processor. If we
         * didn't, we'd never know that the other partition is down and would
         * keep sending IPIs and AMOs to it until the heartbeat times out.
         */
        (void)xp_nofault_PIOR((u64 *)GLOBAL_MMR_ADDR(NASID_GET(&amo->
                                                               variable),
                                                     xp_nofault_PIOR_target));

        local_irq_restore(irq_flags);
}

static void
xpc_indicate_partition_disengaged_sn2(struct xpc_partition *part)
{
        struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;
        unsigned long irq_flags;
        AMO_t *amo = (AMO_t *)__va(part_sn2->remote_amos_page_pa +
                                   (XPC_ENGAGED_PARTITIONS_AMO *
                                    sizeof(AMO_t)));

        local_irq_save(irq_flags);

        /* clear bit corresponding to our partid in remote partition's AMO */
        FETCHOP_STORE_OP(TO_AMO((u64)&amo->variable), FETCHOP_AND,
                         ~(1UL << sn_partition_id));
        /*
         * We must always use the nofault function regardless of whether we
         * are on a Shub 1.1 system or a Shub 1.2 slice 0xc processor. If we
         * didn't, we'd never know that the other partition is down and would
         * keep sending IPIs and AMOs to it until the heartbeat times out.
         */
        (void)xp_nofault_PIOR((u64 *)GLOBAL_MMR_ADDR(NASID_GET(&amo->
                                                               variable),
                                                     xp_nofault_PIOR_target));

        local_irq_restore(irq_flags);

        /*
         * Send activate IRQ to get other side to see that we've cleared our
         * bit in their engaged partitions AMO.
         */
        xpc_activate_IRQ_send_sn2(part_sn2->remote_amos_page_pa,
                                  cnodeid_to_nasid(0),
                                  part_sn2->activate_IRQ_nasid,
                                  part_sn2->activate_IRQ_phys_cpuid);
}

static int
xpc_partition_engaged_sn2(short partid)
{
        AMO_t *amo = xpc_vars->amos_page + XPC_ENGAGED_PARTITIONS_AMO;

        /* our partition's AMO variable ANDed with partid mask */
        return (FETCHOP_LOAD_OP(TO_AMO((u64)&amo->variable), FETCHOP_LOAD) &
                (1UL << partid)) != 0;
}

static int
xpc_any_partition_engaged_sn2(void)
{
        AMO_t *amo = xpc_vars->amos_page + XPC_ENGAGED_PARTITIONS_AMO;

        /* our partition's AMO variable */
        return FETCHOP_LOAD_OP(TO_AMO((u64)&amo->variable), FETCHOP_LOAD) != 0;
}

static void
xpc_assume_partition_disengaged_sn2(short partid)
{
        AMO_t *amo = xpc_vars->amos_page + XPC_ENGAGED_PARTITIONS_AMO;

        /* clear bit(s) based on partid mask in our partition's AMO */
        FETCHOP_STORE_OP(TO_AMO((u64)&amo->variable), FETCHOP_AND,
                         ~(1UL << partid));
}

/* original protection values for each node */
static u64 xpc_prot_vec_sn2[MAX_NUMNODES];

/*
 * Change protections to allow AMO operations on non-Shub 1.1 systems.
 */
static enum xp_retval
xpc_allow_AMO_ops_sn2(AMO_t *amos_page)
{
        u64 nasid_array = 0;
        int ret;

        /*
         * On SHUB 1.1, we cannot call sn_change_memprotect() since the BIST
         * collides with memory operations. On those systems we call
         * xpc_allow_AMO_ops_shub_wars_1_1_sn2() instead.
         */
        if (!enable_shub_wars_1_1()) {
                ret = sn_change_memprotect(ia64_tpa((u64)amos_page), PAGE_SIZE,
                                           SN_MEMPROT_ACCESS_CLASS_1,
                                           &nasid_array);
                if (ret != 0)
                        return xpSalError;
        }
        return xpSuccess;
}

/*
 * Change protections to allow AMO operations on Shub 1.1 systems.
 */
static void
xpc_allow_AMO_ops_shub_wars_1_1_sn2(void)
{
        int node;
        int nasid;

        if (!enable_shub_wars_1_1())
                return;

        for_each_online_node(node) {
                nasid = cnodeid_to_nasid(node);
                /* save current protection values */
                xpc_prot_vec_sn2[node] =
                    (u64)HUB_L((u64 *)GLOBAL_MMR_ADDR(nasid,
                                                  SH1_MD_DQLP_MMR_DIR_PRIVEC0));
                /* open up everything */
                HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid,
                                             SH1_MD_DQLP_MMR_DIR_PRIVEC0),
                      -1UL);
                HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid,
                                             SH1_MD_DQRP_MMR_DIR_PRIVEC0),
                      -1UL);
        }
}

static enum xp_retval
xpc_rsvd_page_init_sn2(struct xpc_rsvd_page *rp)
{
        AMO_t *amos_page;
        int i;
        int ret;

        xpc_vars = XPC_RP_VARS(rp);

        rp->sn.vars_pa = __pa(xpc_vars);

        /* vars_part array follows immediately after vars */
        xpc_vars_part = (struct xpc_vars_part_sn2 *)((u8 *)XPC_RP_VARS(rp) +
                                                     XPC_RP_VARS_SIZE);

        /*
         * Before clearing xpc_vars, see if a page of AMOs had been previously
         * allocated. If not we'll need to allocate one and set permissions
         * so that cross-partition AMOs are allowed.
         *
         * The allocated AMO page needs MCA reporting to remain disabled after
         * XPC has unloaded.  To make this work, we keep a copy of the pointer
         * to this page (i.e., amos_page) in the struct xpc_vars structure,
         * which is pointed to by the reserved page, and re-use that saved copy
         * on subsequent loads of XPC. This AMO page is never freed, and its
         * memory protections are never restricted.
         */
        amos_page = xpc_vars->amos_page;
        if (amos_page == NULL) {
                amos_page = (AMO_t *)TO_AMO(uncached_alloc_page(0, 1));
                if (amos_page == NULL) {
                        dev_err(xpc_part, "can't allocate page of AMOs\n");
                        return xpNoMemory;
                }

                /*
                 * Open up AMO-R/W to cpu.  This is done on Shub 1.1 systems
                 * when xpc_allow_AMO_ops_shub_wars_1_1_sn2() is called.
                 */
                ret = xpc_allow_AMO_ops_sn2(amos_page);
                if (ret != xpSuccess) {
                        dev_err(xpc_part, "can't allow AMO operations\n");
                        uncached_free_page(__IA64_UNCACHED_OFFSET |
                                           TO_PHYS((u64)amos_page), 1);
                        return ret;
                }
        }

        /* clear xpc_vars */
        memset(xpc_vars, 0, sizeof(struct xpc_vars_sn2));

        xpc_vars->version = XPC_V_VERSION;
        xpc_vars->activate_IRQ_nasid = cpuid_to_nasid(0);
        xpc_vars->activate_IRQ_phys_cpuid = cpu_physical_id(0);
        xpc_vars->vars_part_pa = __pa(xpc_vars_part);
        xpc_vars->amos_page_pa = ia64_tpa((u64)amos_page);
        xpc_vars->amos_page = amos_page;        /* save for next load of XPC */

        /* clear xpc_vars_part */
        memset((u64 *)xpc_vars_part, 0, sizeof(struct xpc_vars_part_sn2) *
               xp_max_npartitions);

        /* initialize the activate IRQ related AMO variables */
        for (i = 0; i < xp_nasid_mask_words; i++)
                (void)xpc_IPI_init_sn2(XPC_ACTIVATE_IRQ_AMOS + i);

        /* initialize the engaged remote partitions related AMO variables */
        (void)xpc_IPI_init_sn2(XPC_ENGAGED_PARTITIONS_AMO);
        (void)xpc_IPI_init_sn2(XPC_DEACTIVATE_REQUEST_AMO);

        return xpSuccess;
}

static void
xpc_increment_heartbeat_sn2(void)
{
        xpc_vars->heartbeat++;
}

static void
xpc_offline_heartbeat_sn2(void)
{
        xpc_increment_heartbeat_sn2();
        xpc_vars->heartbeat_offline = 1;
}

static void
xpc_online_heartbeat_sn2(void)
{
        xpc_increment_heartbeat_sn2();
        xpc_vars->heartbeat_offline = 0;
}

static void
xpc_heartbeat_init_sn2(void)
{
        DBUG_ON(xpc_vars == NULL);

        bitmap_zero(xpc_vars->heartbeating_to_mask, XP_MAX_NPARTITIONS_SN2);
        xpc_heartbeating_to_mask = &xpc_vars->heartbeating_to_mask[0];
        xpc_online_heartbeat_sn2();
}

static void
xpc_heartbeat_exit_sn2(void)
{
        xpc_offline_heartbeat_sn2();
}

/*
 * At periodic intervals, scan through all active partitions and ensure
 * their heartbeat is still active.  If not, the partition is deactivated.
 */
static void
xpc_check_remote_hb_sn2(void)
{
        struct xpc_vars_sn2 *remote_vars;
        struct xpc_partition *part;
        short partid;
        enum xp_retval ret;

        remote_vars = (struct xpc_vars_sn2 *)xpc_remote_copy_buffer;

        for (partid = 0; partid < xp_max_npartitions; partid++) {

                if (xpc_exiting)
                        break;

                if (partid == sn_partition_id)
                        continue;

                part = &xpc_partitions[partid];

                if (part->act_state == XPC_P_INACTIVE ||
                    part->act_state == XPC_P_DEACTIVATING) {
                        continue;
                }

                /* pull the remote_hb cache line */
                ret = xp_remote_memcpy(remote_vars,
                                       (void *)part->sn.sn2.remote_vars_pa,
                                       XPC_RP_VARS_SIZE);
                if (ret != xpSuccess) {
                        XPC_DEACTIVATE_PARTITION(part, ret);
                        continue;
                }

                dev_dbg(xpc_part, "partid = %d, heartbeat = %ld, last_heartbeat"
                        " = %ld, heartbeat_offline = %ld, HB_mask[0] = 0x%lx\n",
                        partid, remote_vars->heartbeat, part->last_heartbeat,
                        remote_vars->heartbeat_offline,
                        remote_vars->heartbeating_to_mask[0]);

                if (((remote_vars->heartbeat == part->last_heartbeat) &&
                     (remote_vars->heartbeat_offline == 0)) ||
                    !xpc_hb_allowed(sn_partition_id,
                                    &remote_vars->heartbeating_to_mask)) {

                        XPC_DEACTIVATE_PARTITION(part, xpNoHeartbeat);
                        continue;
                }

                part->last_heartbeat = remote_vars->heartbeat;
        }
}

/*
 * Get a copy of the remote partition's XPC variables from the reserved page.
 *
 * remote_vars points to a buffer that is cacheline aligned for BTE copies and
 * assumed to be of size XPC_RP_VARS_SIZE.
 */
static enum xp_retval
xpc_get_remote_vars_sn2(u64 remote_vars_pa, struct xpc_vars_sn2 *remote_vars)
{
        enum xp_retval ret;

        if (remote_vars_pa == 0)
                return xpVarsNotSet;

        /* pull over the cross partition variables */
        ret = xp_remote_memcpy(remote_vars, (void *)remote_vars_pa,
                               XPC_RP_VARS_SIZE);
        if (ret != xpSuccess)
                return ret;

        if (XPC_VERSION_MAJOR(remote_vars->version) !=
            XPC_VERSION_MAJOR(XPC_V_VERSION)) {
                return xpBadVersion;
        }

        return xpSuccess;
}

static void
xpc_request_partition_activation_sn2(struct xpc_rsvd_page *remote_rp,
                                     u64 remote_rp_pa, int nasid)
{
        xpc_activate_IRQ_send_local_sn2(nasid);
}

static void
xpc_request_partition_reactivation_sn2(struct xpc_partition *part)
{
        xpc_activate_IRQ_send_local_sn2(part->sn.sn2.activate_IRQ_nasid);
}

static void
xpc_request_partition_deactivation_sn2(struct xpc_partition *part)
{
        struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;
        unsigned long irq_flags;
        AMO_t *amo = (AMO_t *)__va(part_sn2->remote_amos_page_pa +
                                  (XPC_DEACTIVATE_REQUEST_AMO * sizeof(AMO_t)));

        local_irq_save(irq_flags);

        /* set bit corresponding to our partid in remote partition's AMO */
        FETCHOP_STORE_OP(TO_AMO((u64)&amo->variable), FETCHOP_OR,
                         (1UL << sn_partition_id));
        /*
         * We must always use the nofault function regardless of whether we
         * are on a Shub 1.1 system or a Shub 1.2 slice 0xc processor. If we
         * didn't, we'd never know that the other partition is down and would
         * keep sending IPIs and AMOs to it until the heartbeat times out.
         */
        (void)xp_nofault_PIOR((u64 *)GLOBAL_MMR_ADDR(NASID_GET(&amo->
                                                               variable),
                                                     xp_nofault_PIOR_target));

        local_irq_restore(irq_flags);

        /*
         * Send activate IRQ to get other side to see that we've set our
         * bit in their deactivate request AMO.
         */
        xpc_activate_IRQ_send_sn2(part_sn2->remote_amos_page_pa,
                                  cnodeid_to_nasid(0),
                                  part_sn2->activate_IRQ_nasid,
                                  part_sn2->activate_IRQ_phys_cpuid);
}

static void
xpc_cancel_partition_deactivation_request_sn2(struct xpc_partition *part)
{
        unsigned long irq_flags;
        AMO_t *amo = (AMO_t *)__va(part->sn.sn2.remote_amos_page_pa +
                                  (XPC_DEACTIVATE_REQUEST_AMO * sizeof(AMO_t)));

        local_irq_save(irq_flags);

        /* clear bit corresponding to our partid in remote partition's AMO */
        FETCHOP_STORE_OP(TO_AMO((u64)&amo->variable), FETCHOP_AND,
                         ~(1UL << sn_partition_id));
        /*
         * We must always use the nofault function regardless of whether we
         * are on a Shub 1.1 system or a Shub 1.2 slice 0xc processor. If we
         * didn't, we'd never know that the other partition is down and would
         * keep sending IPIs and AMOs to it until the heartbeat times out.
         */
        (void)xp_nofault_PIOR((u64 *)GLOBAL_MMR_ADDR(NASID_GET(&amo->
                                                               variable),
                                                     xp_nofault_PIOR_target));

        local_irq_restore(irq_flags);
}

static int
xpc_partition_deactivation_requested_sn2(short partid)
{
        AMO_t *amo = xpc_vars->amos_page + XPC_DEACTIVATE_REQUEST_AMO;

        /* our partition's AMO variable ANDed with partid mask */
        return (FETCHOP_LOAD_OP(TO_AMO((u64)&amo->variable), FETCHOP_LOAD) &
                (1UL << partid)) != 0;
}

/*
 * Update the remote partition's info.
 */
static void
xpc_update_partition_info_sn2(struct xpc_partition *part, u8 remote_rp_version,
                              unsigned long *remote_rp_stamp, u64 remote_rp_pa,
                              u64 remote_vars_pa,
                              struct xpc_vars_sn2 *remote_vars)
{
        struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;

        part->remote_rp_version = remote_rp_version;
        dev_dbg(xpc_part, "  remote_rp_version = 0x%016x\n",
                part->remote_rp_version);

        part->remote_rp_stamp = *remote_rp_stamp;
        dev_dbg(xpc_part, "  remote_rp_stamp = 0x%016lx\n",
                part->remote_rp_stamp);

        part->remote_rp_pa = remote_rp_pa;
        dev_dbg(xpc_part, "  remote_rp_pa = 0x%016lx\n", part->remote_rp_pa);

        part_sn2->remote_vars_pa = remote_vars_pa;
        dev_dbg(xpc_part, "  remote_vars_pa = 0x%016lx\n",
                part_sn2->remote_vars_pa);

        part->last_heartbeat = remote_vars->heartbeat;
        dev_dbg(xpc_part, "  last_heartbeat = 0x%016lx\n",
                part->last_heartbeat);

        part_sn2->remote_vars_part_pa = remote_vars->vars_part_pa;
        dev_dbg(xpc_part, "  remote_vars_part_pa = 0x%016lx\n",
                part_sn2->remote_vars_part_pa);

        part_sn2->activate_IRQ_nasid = remote_vars->activate_IRQ_nasid;
        dev_dbg(xpc_part, "  activate_IRQ_nasid = 0x%x\n",
                part_sn2->activate_IRQ_nasid);

        part_sn2->activate_IRQ_phys_cpuid =
            remote_vars->activate_IRQ_phys_cpuid;
        dev_dbg(xpc_part, "  activate_IRQ_phys_cpuid = 0x%x\n",
                part_sn2->activate_IRQ_phys_cpuid);

        part_sn2->remote_amos_page_pa = remote_vars->amos_page_pa;
        dev_dbg(xpc_part, "  remote_amos_page_pa = 0x%lx\n",
                part_sn2->remote_amos_page_pa);

        part_sn2->remote_vars_version = remote_vars->version;
        dev_dbg(xpc_part, "  remote_vars_version = 0x%x\n",
                part_sn2->remote_vars_version);
}

/*
 * Prior code has determined the nasid which generated an IPI.  Inspect
 * that nasid to determine if its partition needs to be activated or
 * deactivated.
 *
 * A partition is consider "awaiting activation" if our partition
 * flags indicate it is not active and it has a heartbeat.  A
 * partition is considered "awaiting deactivation" if our partition
 * flags indicate it is active but it has no heartbeat or it is not
 * sending its heartbeat to us.
 *
 * To determine the heartbeat, the remote nasid must have a properly
 * initialized reserved page.
 */
static void
xpc_identify_activate_IRQ_req_sn2(int nasid)
{
        struct xpc_rsvd_page *remote_rp;
        struct xpc_vars_sn2 *remote_vars;
        u64 remote_rp_pa;
        u64 remote_vars_pa;
        int remote_rp_version;
        int reactivate = 0;
        unsigned long remote_rp_stamp = 0;
        short partid;
        struct xpc_partition *part;
        struct xpc_partition_sn2 *part_sn2;
        enum xp_retval ret;

        /* pull over the reserved page structure */

        remote_rp = (struct xpc_rsvd_page *)xpc_remote_copy_buffer;

        ret = xpc_get_remote_rp(nasid, NULL, remote_rp, &remote_rp_pa);
        if (ret != xpSuccess) {
                dev_warn(xpc_part, "unable to get reserved page from nasid %d, "
                         "which sent interrupt, reason=%d\n", nasid, ret);
                return;
        }

        remote_vars_pa = remote_rp->sn.vars_pa;
        remote_rp_version = remote_rp->version;
        remote_rp_stamp = remote_rp->stamp;

        partid = remote_rp->SAL_partid;
        part = &xpc_partitions[partid];
        part_sn2 = &part->sn.sn2;

        /* pull over the cross partition variables */

        remote_vars = (struct xpc_vars_sn2 *)xpc_remote_copy_buffer;

        ret = xpc_get_remote_vars_sn2(remote_vars_pa, remote_vars);
        if (ret != xpSuccess) {
                dev_warn(xpc_part, "unable to get XPC variables from nasid %d, "
                         "which sent interrupt, reason=%d\n", nasid, ret);

                XPC_DEACTIVATE_PARTITION(part, ret);
                return;
        }

        part->activate_IRQ_rcvd++;

        dev_dbg(xpc_part, "partid for nasid %d is %d; IRQs = %d; HB = "
                "%ld:0x%lx\n", (int)nasid, (int)partid, part->activate_IRQ_rcvd,
                remote_vars->heartbeat, remote_vars->heartbeating_to_mask[0]);

        if (xpc_partition_disengaged(part) &&
            part->act_state == XPC_P_INACTIVE) {

                xpc_update_partition_info_sn2(part, remote_rp_version,
                                              &remote_rp_stamp, remote_rp_pa,
                                              remote_vars_pa, remote_vars);

                if (xpc_partition_deactivation_requested_sn2(partid)) {
                        /*
                         * Other side is waiting on us to deactivate even though
                         * we already have.
                         */
                        return;
                }

                xpc_activate_partition(part);
                return;
        }

        DBUG_ON(part->remote_rp_version == 0);
        DBUG_ON(part_sn2->remote_vars_version == 0);

        if (remote_rp_stamp != part->remote_rp_stamp) {

                /* the other side rebooted */

                DBUG_ON(xpc_partition_engaged_sn2(partid));
                DBUG_ON(xpc_partition_deactivation_requested_sn2(partid));

                xpc_update_partition_info_sn2(part, remote_rp_version,
                                              &remote_rp_stamp, remote_rp_pa,
                                              remote_vars_pa, remote_vars);
                reactivate = 1;
        }

        if (part->disengage_timeout > 0 && !xpc_partition_disengaged(part)) {
                /* still waiting on other side to disengage from us */
                return;
        }

        if (reactivate)
                XPC_DEACTIVATE_PARTITION(part, xpReactivating);
        else if (xpc_partition_deactivation_requested_sn2(partid))
                XPC_DEACTIVATE_PARTITION(part, xpOtherGoingDown);
}

/*
 * Loop through the activation AMO variables and process any bits
 * which are set.  Each bit indicates a nasid sending a partition
 * activation or deactivation request.
 *
 * Return #of IRQs detected.
 */
int
xpc_identify_activate_IRQ_sender_sn2(void)
{
        int word, bit;
        u64 nasid_mask;
        u64 nasid;              /* remote nasid */
        int n_IRQs_detected = 0;
        AMO_t *act_amos;

        act_amos = xpc_vars->amos_page + XPC_ACTIVATE_IRQ_AMOS;

        /* scan through act AMO variable looking for non-zero entries */
        for (word = 0; word < xp_nasid_mask_words; word++) {

                if (xpc_exiting)
                        break;

                nasid_mask = xpc_IPI_receive_sn2(&act_amos[word]);
                if (nasid_mask == 0) {
                        /* no IRQs from nasids in this variable */
                        continue;
                }

                dev_dbg(xpc_part, "AMO[%d] gave back 0x%lx\n", word,
                        nasid_mask);

                /*
                 * If this nasid has been added to the machine since
                 * our partition was reset, this will retain the
                 * remote nasid in our reserved pages machine mask.
                 * This is used in the event of module reload.
                 */
                xpc_mach_nasids[word] |= nasid_mask;

                /* locate the nasid(s) which sent interrupts */

                for (bit = 0; bit < (8 * sizeof(u64)); bit++) {
                        if (nasid_mask & (1UL << bit)) {
                                n_IRQs_detected++;
                                nasid = XPC_NASID_FROM_W_B(word, bit);
                                dev_dbg(xpc_part, "interrupt from nasid %ld\n",
                                        nasid);
                                xpc_identify_activate_IRQ_req_sn2(nasid);
                        }
                }
        }
        return n_IRQs_detected;
}

static void
xpc_process_activate_IRQ_rcvd_sn2(int n_IRQs_expected)
{
        int n_IRQs_detected;

        n_IRQs_detected = xpc_identify_activate_IRQ_sender_sn2();
        if (n_IRQs_detected < n_IRQs_expected) {
                /* retry once to help avoid missing AMO */
                (void)xpc_identify_activate_IRQ_sender_sn2();
        }
}

/*
 * Setup the infrastructure necessary to support XPartition Communication
 * between the specified remote partition and the local one.
 */
static enum xp_retval
xpc_setup_infrastructure_sn2(struct xpc_partition *part)
{
        struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;
        enum xp_retval retval;
        int ret;
        int cpuid;
        int ch_number;
        struct xpc_channel *ch;
        struct timer_list *timer;
        short partid = XPC_PARTID(part);

        /*
         * Allocate all of the channel structures as a contiguous chunk of
         * memory.
         */
        DBUG_ON(part->channels != NULL);
        part->channels = kzalloc(sizeof(struct xpc_channel) * XPC_MAX_NCHANNELS,
                                 GFP_KERNEL);
        if (part->channels == NULL) {
                dev_err(xpc_chan, "can't get memory for channels\n");
                return xpNoMemory;
        }

        /* allocate all the required GET/PUT values */

        part_sn2->local_GPs = xpc_kzalloc_cacheline_aligned(XPC_GP_SIZE,
                                                            GFP_KERNEL,
                                                            &part_sn2->
                                                            local_GPs_base);
        if (part_sn2->local_GPs == NULL) {
                dev_err(xpc_chan, "can't get memory for local get/put "
                        "values\n");
                retval = xpNoMemory;
                goto out_1;
        }

        part_sn2->remote_GPs = xpc_kzalloc_cacheline_aligned(XPC_GP_SIZE,
                                                             GFP_KERNEL,
                                                             &part_sn2->
                                                             remote_GPs_base);
        if (part_sn2->remote_GPs == NULL) {
                dev_err(xpc_chan, "can't get memory for remote get/put "
                        "values\n");
                retval = xpNoMemory;
                goto out_2;
        }

        part_sn2->remote_GPs_pa = 0;

        /* allocate all the required open and close args */

        part->local_openclose_args =
            xpc_kzalloc_cacheline_aligned(XPC_OPENCLOSE_ARGS_SIZE, GFP_KERNEL,
                                          &part->local_openclose_args_base);
        if (part->local_openclose_args == NULL) {
                dev_err(xpc_chan, "can't get memory for local connect args\n");
                retval = xpNoMemory;
                goto out_3;
        }

        part->remote_openclose_args =
            xpc_kzalloc_cacheline_aligned(XPC_OPENCLOSE_ARGS_SIZE, GFP_KERNEL,
                                          &part->remote_openclose_args_base);
        if (part->remote_openclose_args == NULL) {
                dev_err(xpc_chan, "can't get memory for remote connect args\n");
                retval = xpNoMemory;
                goto out_4;
        }

        part_sn2->remote_openclose_args_pa = 0;

        part_sn2->local_IPI_amo_va = xpc_IPI_init_sn2(partid);
        part->local_IPI_amo = 0;
        spin_lock_init(&part->IPI_lock);

        part_sn2->remote_IPI_nasid = 0;
        part_sn2->remote_IPI_phys_cpuid = 0;
        part_sn2->remote_IPI_amo_va = NULL;

        atomic_set(&part->channel_mgr_requests, 1);
        init_waitqueue_head(&part->channel_mgr_wq);

        sprintf(part_sn2->IPI_owner, "xpc%02d", partid);
        ret = request_irq(SGI_XPC_NOTIFY, xpc_handle_notify_IRQ_sn2,
                          IRQF_SHARED, part_sn2->IPI_owner,
                          (void *)(u64)partid);
        if (ret != 0) {
                dev_err(xpc_chan, "can't register NOTIFY IRQ handler, "
                        "errno=%d\n", -ret);
                retval = xpLackOfResources;
                goto out_5;
        }

        /* Setup a timer to check for dropped IPIs */
        timer = &part_sn2->dropped_notify_IRQ_timer;
        init_timer(timer);
        timer->function =
            (void (*)(unsigned long))xpc_dropped_notify_IRQ_check_sn2;
        timer->data = (unsigned long)part;
        timer->expires = jiffies + XPC_P_DROPPED_IPI_WAIT_INTERVAL;
        add_timer(timer);

        part->nchannels = XPC_MAX_NCHANNELS;

        atomic_set(&part->nchannels_active, 0);
        atomic_set(&part->nchannels_engaged, 0);

        for (ch_number = 0; ch_number < part->nchannels; ch_number++) {
                ch = &part->channels[ch_number];

                ch->partid = partid;
                ch->number = ch_number;
                ch->flags = XPC_C_DISCONNECTED;

                ch->sn.sn2.local_GP = &part_sn2->local_GPs[ch_number];
                ch->local_openclose_args =
                    &part->local_openclose_args[ch_number];

                atomic_set(&ch->kthreads_assigned, 0);
                atomic_set(&ch->kthreads_idle, 0);
                atomic_set(&ch->kthreads_active, 0);

                atomic_set(&ch->references, 0);
                atomic_set(&ch->n_to_notify, 0);

                spin_lock_init(&ch->lock);
                mutex_init(&ch->sn.sn2.msg_to_pull_mutex);
                init_completion(&ch->wdisconnect_wait);

                atomic_set(&ch->n_on_msg_allocate_wq, 0);
                init_waitqueue_head(&ch->msg_allocate_wq);
                init_waitqueue_head(&ch->idle_wq);
        }

        /*
         * With the setting of the partition setup_state to XPC_P_SETUP, we're
         * declaring that this partition is ready to go.
         */
        part->setup_state = XPC_P_SETUP;

        /*
         * Setup the per partition specific variables required by the
         * remote partition to establish channel connections with us.
         *
         * The setting of the magic # indicates that these per partition
         * specific variables are ready to be used.
         */
        xpc_vars_part[partid].GPs_pa = __pa(part_sn2->local_GPs);
        xpc_vars_part[partid].openclose_args_pa =
            __pa(part->local_openclose_args);
        xpc_vars_part[partid].IPI_amo_pa = __pa(part_sn2->local_IPI_amo_va);
        cpuid = raw_smp_processor_id(); /* any CPU in this partition will do */
        xpc_vars_part[partid].IPI_nasid = cpuid_to_nasid(cpuid);
        xpc_vars_part[partid].IPI_phys_cpuid = cpu_physical_id(cpuid);
        xpc_vars_part[partid].nchannels = part->nchannels;
        xpc_vars_part[partid].magic = XPC_VP_MAGIC1;

        return xpSuccess;

        /* setup of infrastructure failed */
out_5:
        kfree(part->remote_openclose_args_base);
        part->remote_openclose_args = NULL;
out_4:
        kfree(part->local_openclose_args_base);
        part->local_openclose_args = NULL;
out_3:
        kfree(part_sn2->remote_GPs_base);
        part_sn2->remote_GPs = NULL;
out_2:
        kfree(part_sn2->local_GPs_base);
        part_sn2->local_GPs = NULL;
out_1:
        kfree(part->channels);
        part->channels = NULL;
        return retval;
}

/*
 * Teardown the infrastructure necessary to support XPartition Communication
 * between the specified remote partition and the local one.
 */
static void
xpc_teardown_infrastructure_sn2(struct xpc_partition *part)
{
        struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;
        short partid = XPC_PARTID(part);

        /*
         * We start off by making this partition inaccessible to local
         * processes by marking it as no longer setup. Then we make it
         * inaccessible to remote processes by clearing the XPC per partition
         * specific variable's magic # (which indicates that these variables
         * are no longer valid) and by ignoring all XPC notify IPIs sent to
         * this partition.
         */

        DBUG_ON(atomic_read(&part->nchannels_engaged) != 0);
        DBUG_ON(atomic_read(&part->nchannels_active) != 0);
        DBUG_ON(part->setup_state != XPC_P_SETUP);
        part->setup_state = XPC_P_WTEARDOWN;

        xpc_vars_part[partid].magic = 0;

        free_irq(SGI_XPC_NOTIFY, (void *)(u64)partid);

        /*
         * Before proceeding with the teardown we have to wait until all
         * existing references cease.
         */
        wait_event(part->teardown_wq, (atomic_read(&part->references) == 0));

        /* now we can begin tearing down the infrastructure */

        part->setup_state = XPC_P_TORNDOWN;

        /* in case we've still got outstanding timers registered... */
        del_timer_sync(&part_sn2->dropped_notify_IRQ_timer);

        kfree(part->remote_openclose_args_base);
        part->remote_openclose_args = NULL;
        kfree(part->local_openclose_args_base);
        part->local_openclose_args = NULL;
        kfree(part_sn2->remote_GPs_base);
        part_sn2->remote_GPs = NULL;
        kfree(part_sn2->local_GPs_base);
        part_sn2->local_GPs = NULL;
        kfree(part->channels);
        part->channels = NULL;
        part_sn2->local_IPI_amo_va = NULL;
}

/*
 * Create a wrapper that hides the underlying mechanism for pulling a cacheline
 * (or multiple cachelines) from a remote partition.
 *
 * src must be a cacheline aligned physical address on the remote partition.
 * dst must be a cacheline aligned virtual address on this partition.
 * cnt must be cacheline sized
 */
/* >>> Replace this function by call to xp_remote_memcpy() or bte_copy()? */
static enum xp_retval
xpc_pull_remote_cachelines_sn2(struct xpc_partition *part, void *dst,
                               const void *src, size_t cnt)
{
        enum xp_retval ret;

        DBUG_ON((u64)src != L1_CACHE_ALIGN((u64)src));
        DBUG_ON((u64)dst != L1_CACHE_ALIGN((u64)dst));
        DBUG_ON(cnt != L1_CACHE_ALIGN(cnt));

        if (part->act_state == XPC_P_DEACTIVATING)
                return part->reason;

        ret = xp_remote_memcpy(dst, src, cnt);
        if (ret != xpSuccess) {
                dev_dbg(xpc_chan, "xp_remote_memcpy() from partition %d failed,"
                        " ret=%d\n", XPC_PARTID(part), ret);
        }
        return ret;
}

/*
 * Pull the remote per partition specific variables from the specified
 * partition.
 */
static enum xp_retval
xpc_pull_remote_vars_part_sn2(struct xpc_partition *part)
{
        struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;
        u8 buffer[L1_CACHE_BYTES * 2];
        struct xpc_vars_part_sn2 *pulled_entry_cacheline =
            (struct xpc_vars_part_sn2 *)L1_CACHE_ALIGN((u64)buffer);
        struct xpc_vars_part_sn2 *pulled_entry;
        u64 remote_entry_cacheline_pa, remote_entry_pa;
        short partid = XPC_PARTID(part);
        enum xp_retval ret;

        /* pull the cacheline that contains the variables we're interested in */

        DBUG_ON(part_sn2->remote_vars_part_pa !=
                L1_CACHE_ALIGN(part_sn2->remote_vars_part_pa));
        DBUG_ON(sizeof(struct xpc_vars_part_sn2) != L1_CACHE_BYTES / 2);

        remote_entry_pa = part_sn2->remote_vars_part_pa +
            sn_partition_id * sizeof(struct xpc_vars_part_sn2);

        remote_entry_cacheline_pa = (remote_entry_pa & ~(L1_CACHE_BYTES - 1));

        pulled_entry = (struct xpc_vars_part_sn2 *)((u64)pulled_entry_cacheline
                                                    + (remote_entry_pa &
                                                    (L1_CACHE_BYTES - 1)));

        ret = xpc_pull_remote_cachelines_sn2(part, pulled_entry_cacheline,
                                             (void *)remote_entry_cacheline_pa,
                                             L1_CACHE_BYTES);
        if (ret != xpSuccess) {
                dev_dbg(xpc_chan, "failed to pull XPC vars_part from "
                        "partition %d, ret=%d\n", partid, ret);
                return ret;
        }

        /* see if they've been set up yet */

        if (pulled_entry->magic != XPC_VP_MAGIC1 &&
            pulled_entry->magic != XPC_VP_MAGIC2) {

                if (pulled_entry->magic != 0) {
                        dev_dbg(xpc_chan, "partition %d's XPC vars_part for "
                                "partition %d has bad magic value (=0x%lx)\n",
                                partid, sn_partition_id, pulled_entry->magic);
                        return xpBadMagic;
                }

                /* they've not been initialized yet */
                return xpRetry;
        }

        if (xpc_vars_part[partid].magic == XPC_VP_MAGIC1) {

                /* validate the variables */

                if (pulled_entry->GPs_pa == 0 ||
                    pulled_entry->openclose_args_pa == 0 ||
                    pulled_entry->IPI_amo_pa == 0) {

                        dev_err(xpc_chan, "partition %d's XPC vars_part for "
                                "partition %d are not valid\n", partid,
                                sn_partition_id);
                        return xpInvalidAddress;
                }

                /* the variables we imported look to be valid */

                part_sn2->remote_GPs_pa = pulled_entry->GPs_pa;
                part_sn2->remote_openclose_args_pa =
                    pulled_entry->openclose_args_pa;
                part_sn2->remote_IPI_amo_va =
                    (AMO_t *)__va(pulled_entry->IPI_amo_pa);
                part_sn2->remote_IPI_nasid = pulled_entry->IPI_nasid;
                part_sn2->remote_IPI_phys_cpuid = pulled_entry->IPI_phys_cpuid;

                if (part->nchannels > pulled_entry->nchannels)
                        part->nchannels = pulled_entry->nchannels;

                /* let the other side know that we've pulled their variables */

                xpc_vars_part[partid].magic = XPC_VP_MAGIC2;
        }

        if (pulled_entry->magic == XPC_VP_MAGIC1)
                return xpRetry;

        return xpSuccess;
}

/*
 * Establish first contact with the remote partititon. This involves pulling
 * the XPC per partition variables from the remote partition and waiting for
 * the remote partition to pull ours.
 */
static enum xp_retval
xpc_make_first_contact_sn2(struct xpc_partition *part)
{
        struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;
        enum xp_retval ret;

        /*
         * Register the remote partition's AMOs with SAL so it can handle
         * and cleanup errors within that address range should the remote
         * partition go down. We don't unregister this range because it is
         * difficult to tell when outstanding writes to the remote partition
         * are finished and thus when it is safe to unregister. This should
         * not result in wasted space in the SAL xp_addr_region table because
         * we should get the same page for remote_amos_page_pa after module
         * reloads and system reboots.
         */
        if (sn_register_xp_addr_region(part_sn2->remote_amos_page_pa,
                                       PAGE_SIZE, 1) < 0) {
                dev_warn(xpc_part, "xpc_activating(%d) failed to register "
                         "xp_addr region\n", XPC_PARTID(part));

                ret = xpPhysAddrRegFailed;
                XPC_DEACTIVATE_PARTITION(part, ret);
                return ret;
        }

        /*
         * Send activate IRQ to get other side to activate if they've not
         * already begun to do so.
         */
        xpc_activate_IRQ_send_sn2(part_sn2->remote_amos_page_pa,
                                  cnodeid_to_nasid(0),
                                  part_sn2->activate_IRQ_nasid,
                                  part_sn2->activate_IRQ_phys_cpuid);

        while ((ret = xpc_pull_remote_vars_part_sn2(part)) != xpSuccess) {
                if (ret != xpRetry) {
                        XPC_DEACTIVATE_PARTITION(part, ret);
                        return ret;
                }

                dev_dbg(xpc_part, "waiting to make first contact with "
                        "partition %d\n", XPC_PARTID(part));

                /* wait a 1/4 of a second or so */
                (void)msleep_interruptible(250);

                if (part->act_state == XPC_P_DEACTIVATING)
                        return part->reason;
        }

        return xpSuccess;
}

/*
 * Get the IPI flags and pull the openclose args and/or remote GPs as needed.
 */
static u64
xpc_get_IPI_flags_sn2(struct xpc_partition *part)
{
        struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;
        unsigned long irq_flags;
        u64 IPI_amo;
        enum xp_retval ret;

        /*
         * See if there are any IPI flags to be handled.
         */

        spin_lock_irqsave(&part->IPI_lock, irq_flags);
        IPI_amo = part->local_IPI_amo;
        if (IPI_amo != 0)
                part->local_IPI_amo = 0;

        spin_unlock_irqrestore(&part->IPI_lock, irq_flags);

        if (XPC_ANY_OPENCLOSE_IPI_FLAGS_SET(IPI_amo)) {
                ret = xpc_pull_remote_cachelines_sn2(part, part->
                                                     remote_openclose_args,
                                                     (void *)part_sn2->
                                                     remote_openclose_args_pa,
                                                     XPC_OPENCLOSE_ARGS_SIZE);
                if (ret != xpSuccess) {
                        XPC_DEACTIVATE_PARTITION(part, ret);

                        dev_dbg(xpc_chan, "failed to pull openclose args from "
                                "partition %d, ret=%d\n", XPC_PARTID(part),
                                ret);

                        /* don't bother processing IPIs anymore */
                        IPI_amo = 0;
                }
        }

        if (XPC_ANY_MSG_IPI_FLAGS_SET(IPI_amo)) {
                ret = xpc_pull_remote_cachelines_sn2(part, part_sn2->remote_GPs,
                                                (void *)part_sn2->remote_GPs_pa,
                                                     XPC_GP_SIZE);
                if (ret != xpSuccess) {
                        XPC_DEACTIVATE_PARTITION(part, ret);

                        dev_dbg(xpc_chan, "failed to pull GPs from partition "
                                "%d, ret=%d\n", XPC_PARTID(part), ret);

                        /* don't bother processing IPIs anymore */
                        IPI_amo = 0;
                }
        }

        return IPI_amo;
}

/*
 * Notify those who wanted to be notified upon delivery of their message.
 */
static void
xpc_notify_senders_sn2(struct xpc_channel *ch, enum xp_retval reason, s64 put)
{
        struct xpc_notify *notify;
        u8 notify_type;
        s64 get = ch->sn.sn2.w_remote_GP.get - 1;

        while (++get < put && atomic_read(&ch->n_to_notify) > 0) {

                notify = &ch->notify_queue[get % ch->local_nentries];

                /*
                 * See if the notify entry indicates it was associated with
                 * a message who's sender wants to be notified. It is possible
                 * that it is, but someone else is doing or has done the
                 * notification.
                 */
                notify_type = notify->type;
                if (notify_type == 0 ||
                    cmpxchg(&notify->type, notify_type, 0) != notify_type) {
                        continue;
                }

                DBUG_ON(notify_type != XPC_N_CALL);

                atomic_dec(&ch->n_to_notify);

                if (notify->func != NULL) {
                        dev_dbg(xpc_chan, "notify->func() called, notify=0x%p, "
                                "msg_number=%ld, partid=%d, channel=%d\n",
                                (void *)notify, get, ch->partid, ch->number);

                        notify->func(reason, ch->partid, ch->number,
                                     notify->key);

                        dev_dbg(xpc_chan, "notify->func() returned, "
                                "notify=0x%p, msg_number=%ld, partid=%d, "
                                "channel=%d\n", (void *)notify, get,
                                ch->partid, ch->number);
                }
        }
}

static void
xpc_notify_senders_of_disconnect_sn2(struct xpc_channel *ch)
{
        xpc_notify_senders_sn2(ch, ch->reason, ch->sn.sn2.w_local_GP.put);
}

/*
 * Clear some of the msg flags in the local message queue.
 */
static inline void
xpc_clear_local_msgqueue_flags_sn2(struct xpc_channel *ch)
{
        struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
        struct xpc_msg *msg;
        s64 get;

        get = ch_sn2->w_remote_GP.get;
        do {
                msg = (struct xpc_msg *)((u64)ch->local_msgqueue +
                                         (get % ch->local_nentries) *
                                         ch->msg_size);
                msg->flags = 0;
        } while (++get < ch_sn2->remote_GP.get);
}

/*
 * Clear some of the msg flags in the remote message queue.
 */
static inline void
xpc_clear_remote_msgqueue_flags_sn2(struct xpc_channel *ch)
{
        struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
        struct xpc_msg *msg;
        s64 put;

        put = ch_sn2->w_remote_GP.put;
        do {
                msg = (struct xpc_msg *)((u64)ch->remote_msgqueue +
                                         (put % ch->remote_nentries) *
                                         ch->msg_size);
                msg->flags = 0;
        } while (++put < ch_sn2->remote_GP.put);
}

static void
xpc_process_msg_IPI_sn2(struct xpc_partition *part, int ch_number)
{
        struct xpc_channel *ch = &part->channels[ch_number];
        struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
        int nmsgs_sent;

        ch_sn2->remote_GP = part->sn.sn2.remote_GPs[ch_number];

        /* See what, if anything, has changed for each connected channel */

        xpc_msgqueue_ref(ch);

        if (ch_sn2->w_remote_GP.get == ch_sn2->remote_GP.get &&
            ch_sn2->w_remote_GP.put == ch_sn2->remote_GP.put) {
                /* nothing changed since GPs were last pulled */
                xpc_msgqueue_deref(ch);
                return;
        }

        if (!(ch->flags & XPC_C_CONNECTED)) {
                xpc_msgqueue_deref(ch);
                return;
        }

        /*
         * First check to see if messages recently sent by us have been
         * received by the other side. (The remote GET value will have
         * changed since we last looked at it.)
         */

        if (ch_sn2->w_remote_GP.get != ch_sn2->remote_GP.get) {

                /*
                 * We need to notify any senders that want to be notified
                 * that their sent messages have been received by their
                 * intended recipients. We need to do this before updating
                 * w_remote_GP.get so that we don't allocate the same message
                 * queue entries prematurely (see xpc_allocate_msg()).
                 */
                if (atomic_read(&ch->n_to_notify) > 0) {
                        /*
                         * Notify senders that messages sent have been
                         * received and delivered by the other side.
                         */
                        xpc_notify_senders_sn2(ch, xpMsgDelivered,
                                               ch_sn2->remote_GP.get);
                }

                /*
                 * Clear msg->flags in previously sent messages, so that
                 * they're ready for xpc_allocate_msg().
                 */
                xpc_clear_local_msgqueue_flags_sn2(ch);

                ch_sn2->w_remote_GP.get = ch_sn2->remote_GP.get;

                dev_dbg(xpc_chan, "w_remote_GP.get changed to %ld, partid=%d, "
                        "channel=%d\n", ch_sn2->w_remote_GP.get, ch->partid,
                        ch->number);

                /*
                 * If anyone was waiting for message queue entries to become
                 * available, wake them up.
                 */
                if (atomic_read(&ch->n_on_msg_allocate_wq) > 0)
                        wake_up(&ch->msg_allocate_wq);
        }

        /*
         * Now check for newly sent messages by the other side. (The remote
         * PUT value will have changed since we last looked at it.)
         */

        if (ch_sn2->w_remote_GP.put != ch_sn2->remote_GP.put) {
                /*
                 * Clear msg->flags in previously received messages, so that
                 * they're ready for xpc_get_deliverable_msg().
                 */
                xpc_clear_remote_msgqueue_flags_sn2(ch);

                ch_sn2->w_remote_GP.put = ch_sn2->remote_GP.put;

                dev_dbg(xpc_chan, "w_remote_GP.put changed to %ld, partid=%d, "
                        "channel=%d\n", ch_sn2->w_remote_GP.put, ch->partid,
                        ch->number);

                nmsgs_sent = ch_sn2->w_remote_GP.put - ch_sn2->w_local_GP.get;
                if (nmsgs_sent > 0) {
                        dev_dbg(xpc_chan, "msgs waiting to be copied and "
                                "delivered=%d, partid=%d, channel=%d\n",
                                nmsgs_sent, ch->partid, ch->number);

                        if (ch->flags & XPC_C_CONNECTEDCALLOUT_MADE)
                                xpc_activate_kthreads(ch, nmsgs_sent);
                }
        }

        xpc_msgqueue_deref(ch);
}

static struct xpc_msg *
xpc_pull_remote_msg_sn2(struct xpc_channel *ch, s64 get)
{
        struct xpc_partition *part = &xpc_partitions[ch->partid];
        struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
        struct xpc_msg *remote_msg, *msg;
        u32 msg_index, nmsgs;
        u64 msg_offset;
        enum xp_retval ret;

        if (mutex_lock_interruptible(&ch_sn2->msg_to_pull_mutex) != 0) {
                /* we were interrupted by a signal */
                return NULL;
        }

        while (get >= ch_sn2->next_msg_to_pull) {

                /* pull as many messages as are ready and able to be pulled */

                msg_index = ch_sn2->next_msg_to_pull % ch->remote_nentries;

                DBUG_ON(ch_sn2->next_msg_to_pull >= ch_sn2->w_remote_GP.put);
                nmsgs = ch_sn2->w_remote_GP.put - ch_sn2->next_msg_to_pull;
                if (msg_index + nmsgs > ch->remote_nentries) {
                        /* ignore the ones that wrap the msg queue for now */
                        nmsgs = ch->remote_nentries - msg_index;
                }

                msg_offset = msg_index * ch->msg_size;
                msg = (struct xpc_msg *)((u64)ch->remote_msgqueue + msg_offset);
                remote_msg = (struct xpc_msg *)(ch->remote_msgqueue_pa +
                                                msg_offset);

                ret = xpc_pull_remote_cachelines_sn2(part, msg, remote_msg,
                                                     nmsgs * ch->msg_size);
                if (ret != xpSuccess) {

                        dev_dbg(xpc_chan, "failed to pull %d msgs starting with"
                                " msg %ld from partition %d, channel=%d, "
                                "ret=%d\n", nmsgs, ch_sn2->next_msg_to_pull,
                                ch->partid, ch->number, ret);

                        XPC_DEACTIVATE_PARTITION(part, ret);

                        mutex_unlock(&ch_sn2->msg_to_pull_mutex);
                        return NULL;
                }

                ch_sn2->next_msg_to_pull += nmsgs;
        }

        mutex_unlock(&ch_sn2->msg_to_pull_mutex);

        /* return the message we were looking for */
        msg_offset = (get % ch->remote_nentries) * ch->msg_size;
        msg = (struct xpc_msg *)((u64)ch->remote_msgqueue + msg_offset);

        return msg;
}

static int
xpc_n_of_deliverable_msgs_sn2(struct xpc_channel *ch)
{
        return ch->sn.sn2.w_remote_GP.put - ch->sn.sn2.w_local_GP.get;
}

/*
 * Get a message to be delivered.
 */
static struct xpc_msg *
xpc_get_deliverable_msg_sn2(struct xpc_channel *ch)
{
        struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
        struct xpc_msg *msg = NULL;
        s64 get;

        do {
                if (ch->flags & XPC_C_DISCONNECTING)
                        break;

                get = ch_sn2->w_local_GP.get;
                rmb();  /* guarantee that .get loads before .put */
                if (get == ch_sn2->w_remote_GP.put)
                        break;

                /* There are messages waiting to be pulled and delivered.
                 * We need to try to secure one for ourselves. We'll do this
                 * by trying to increment w_local_GP.get and hope that no one
                 * else beats us to it. If they do, we'll we'll simply have
                 * to try again for the next one.
                 */

                if (cmpxchg(&ch_sn2->w_local_GP.get, get, get + 1) == get) {
                        /* we got the entry referenced by get */

                        dev_dbg(xpc_chan, "w_local_GP.get changed to %ld, "
                                "partid=%d, channel=%d\n", get + 1,
                                ch->partid, ch->number);

                        /* pull the message from the remote partition */

                        msg = xpc_pull_remote_msg_sn2(ch, get);

                        DBUG_ON(msg != NULL && msg->number != get);
                        DBUG_ON(msg != NULL && (msg->flags & XPC_M_DONE));
                        DBUG_ON(msg != NULL && !(msg->flags & XPC_M_READY));

                        break;
                }

        } while (1);

        return msg;
}

/*
 * Now we actually send the messages that are ready to be sent by advancing
 * the local message queue's Put value and then send an IPI to the recipient
 * partition.
 */
static void
xpc_send_msgs_sn2(struct xpc_channel *ch, s64 initial_put)
{
        struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
        struct xpc_msg *msg;
        s64 put = initial_put + 1;
        int send_IPI = 0;

        while (1) {

                while (1) {
                        if (put == ch_sn2->w_local_GP.put)
                                break;

                        msg = (struct xpc_msg *)((u64)ch->local_msgqueue +
                                                 (put % ch->local_nentries) *
                                                 ch->msg_size);

                        if (!(msg->flags & XPC_M_READY))
                                break;

                        put++;
                }

                if (put == initial_put) {
                        /* nothing's changed */
                        break;
                }

                if (cmpxchg_rel(&ch_sn2->local_GP->put, initial_put, put) !=
                    initial_put) {
                        /* someone else beat us to it */
                        DBUG_ON(ch_sn2->local_GP->put < initial_put);
                        break;
                }

                /* we just set the new value of local_GP->put */

                dev_dbg(xpc_chan, "local_GP->put changed to %ld, partid=%d, "
                        "channel=%d\n", put, ch->partid, ch->number);

                send_IPI = 1;

                /*
                 * We need to ensure that the message referenced by
                 * local_GP->put is not XPC_M_READY or that local_GP->put
                 * equals w_local_GP.put, so we'll go have a look.
                 */
                initial_put = put;
        }

        if (send_IPI)
                xpc_send_channel_msgrequest_sn2(ch);
}

/*
 * Allocate an entry for a message from the message queue associated with the
 * specified channel.
 */
static enum xp_retval
xpc_allocate_msg_sn2(struct xpc_channel *ch, u32 flags,
                     struct xpc_msg **address_of_msg)
{
        struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
        struct xpc_msg *msg;
        enum xp_retval ret;
        s64 put;

        /*
         * Get the next available message entry from the local message queue.
         * If none are available, we'll make sure that we grab the latest
         * GP values.
         */
        ret = xpTimeout;

        while (1) {

                put = ch_sn2->w_local_GP.put;
                rmb();  /* guarantee that .put loads before .get */
                if (put - ch_sn2->w_remote_GP.get < ch->local_nentries) {

                        /* There are available message entries. We need to try
                         * to secure one for ourselves. We'll do this by trying
                         * to increment w_local_GP.put as long as someone else
                         * doesn't beat us to it. If they do, we'll have to
                         * try again.
                         */
                        if (cmpxchg(&ch_sn2->w_local_GP.put, put, put + 1) ==
                            put) {
                                /* we got the entry referenced by put */
                                break;
                        }
                        continue;       /* try again */
                }

                /*
                 * There aren't any available msg entries at this time.
                 *
                 * In waiting for a message entry to become available,
                 * we set a timeout in case the other side is not
                 * sending completion IPIs. This lets us fake an IPI
                 * that will cause the IPI handler to fetch the latest
                 * GP values as if an IPI was sent by the other side.
                 */
                if (ret == xpTimeout)
                        xpc_send_channel_local_msgrequest_sn2(ch);

                if (flags & XPC_NOWAIT)
                        return xpNoWait;

                ret = xpc_allocate_msg_wait(ch);
                if (ret != xpInterrupted && ret != xpTimeout)
                        return ret;
        }

        /* get the message's address and initialize it */
        msg = (struct xpc_msg *)((u64)ch->local_msgqueue +
                                 (put % ch->local_nentries) * ch->msg_size);

        DBUG_ON(msg->flags != 0);
        msg->number = put;

        dev_dbg(xpc_chan, "w_local_GP.put changed to %ld; msg=0x%p, "
                "msg_number=%ld, partid=%d, channel=%d\n", put + 1,
                (void *)msg, msg->number, ch->partid, ch->number);

        *address_of_msg = msg;
        return xpSuccess;
}

/*
 * Common code that does the actual sending of the message by advancing the
 * local message queue's Put value and sends an IPI to the partition the
 * message is being sent to.
 */
static enum xp_retval
xpc_send_msg_sn2(struct xpc_channel *ch, u32 flags, void *payload,
                 u16 payload_size, u8 notify_type, xpc_notify_func func,
                 void *key)
{
        enum xp_retval ret = xpSuccess;
        struct xpc_msg *msg = msg;
        struct xpc_notify *notify = notify;
        s64 msg_number;
        s64 put;

        DBUG_ON(notify_type == XPC_N_CALL && func == NULL);

        if (XPC_MSG_SIZE(payload_size) > ch->msg_size)
                return xpPayloadTooBig;

        xpc_msgqueue_ref(ch);

        if (ch->flags & XPC_C_DISCONNECTING) {
                ret = ch->reason;
                goto out_1;
        }
        if (!(ch->flags & XPC_C_CONNECTED)) {
                ret = xpNotConnected;
                goto out_1;
        }

        ret = xpc_allocate_msg_sn2(ch, flags, &msg);
        if (ret != xpSuccess)
                goto out_1;

        msg_number = msg->number;

        if (notify_type != 0) {
                /*
                 * Tell the remote side to send an ACK interrupt when the
                 * message has been delivered.
                 */
                msg->flags |= XPC_M_INTERRUPT;

                atomic_inc(&ch->n_to_notify);

                notify = &ch->notify_queue[msg_number % ch->local_nentries];
                notify->func = func;
                notify->key = key;
                notify->type = notify_type;

                /* >>> is a mb() needed here? */

                if (ch->flags & XPC_C_DISCONNECTING) {
                        /*
                         * An error occurred between our last error check and
                         * this one. We will try to clear the type field from
                         * the notify entry. If we succeed then
                         * xpc_disconnect_channel() didn't already process
                         * the notify entry.
                         */
                        if (cmpxchg(&notify->type, notify_type, 0) ==
                            notify_type) {
                                atomic_dec(&ch->n_to_notify);
                                ret = ch->reason;
                        }
                        goto out_1;
                }
        }

        memcpy(&msg->payload, payload, payload_size);

        msg->flags |= XPC_M_READY;

        /*
         * The preceding store of msg->flags must occur before the following
         * load of local_GP->put.
         */
        mb();

        /* see if the message is next in line to be sent, if so send it */

        put = ch->sn.sn2.local_GP->put;
        if (put == msg_number)
                xpc_send_msgs_sn2(ch, put);

out_1:
        xpc_msgqueue_deref(ch);
        return ret;
}

/*
 * Now we actually acknowledge the messages that have been delivered and ack'd
 * by advancing the cached remote message queue's Get value and if requested
 * send an IPI to the message sender's partition.
 */
static void
xpc_acknowledge_msgs_sn2(struct xpc_channel *ch, s64 initial_get, u8 msg_flags)
{
        struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
        struct xpc_msg *msg;
        s64 get = initial_get + 1;
        int send_IPI = 0;

        while (1) {

                while (1) {
                        if (get == ch_sn2->w_local_GP.get)
                                break;

                        msg = (struct xpc_msg *)((u64)ch->remote_msgqueue +
                                                 (get % ch->remote_nentries) *
                                                 ch->msg_size);

                        if (!(msg->flags & XPC_M_DONE))
                                break;

                        msg_flags |= msg->flags;
                        get++;
                }

                if (get == initial_get) {
                        /* nothing's changed */
                        break;
                }

                if (cmpxchg_rel(&ch_sn2->local_GP->get, initial_get, get) !=
                    initial_get) {
                        /* someone else beat us to it */
                        DBUG_ON(ch_sn2->local_GP->get <= initial_get);
                        break;
                }

                /* we just set the new value of local_GP->get */

                dev_dbg(xpc_chan, "local_GP->get changed to %ld, partid=%d, "
                        "channel=%d\n", get, ch->partid, ch->number);

                send_IPI = (msg_flags & XPC_M_INTERRUPT);

                /*
                 * We need to ensure that the message referenced by
                 * local_GP->get is not XPC_M_DONE or that local_GP->get
                 * equals w_local_GP.get, so we'll go have a look.
                 */
                initial_get = get;
        }

        if (send_IPI)
                xpc_send_channel_msgrequest_sn2(ch);
}

static void
xpc_received_msg_sn2(struct xpc_channel *ch, struct xpc_msg *msg)
{
        s64 get;
        s64 msg_number = msg->number;

        dev_dbg(xpc_chan, "msg=0x%p, msg_number=%ld, partid=%d, channel=%d\n",
                (void *)msg, msg_number, ch->partid, ch->number);

        DBUG_ON((((u64)msg - (u64)ch->remote_msgqueue) / ch->msg_size) !=
                msg_number % ch->remote_nentries);
        DBUG_ON(msg->flags & XPC_M_DONE);

        msg->flags |= XPC_M_DONE;

        /*
         * The preceding store of msg->flags must occur before the following
         * load of local_GP->get.
         */
        mb();

        /*
         * See if this message is next in line to be acknowledged as having
         * been delivered.
         */
        get = ch->sn.sn2.local_GP->get;
        if (get == msg_number)
                xpc_acknowledge_msgs_sn2(ch, get, msg->flags);
}

int
xpc_init_sn2(void)
{
        int ret;

        xpc_rsvd_page_init = xpc_rsvd_page_init_sn2;
        xpc_increment_heartbeat = xpc_increment_heartbeat_sn2;
        xpc_offline_heartbeat = xpc_offline_heartbeat_sn2;
        xpc_online_heartbeat = xpc_online_heartbeat_sn2;
        xpc_heartbeat_init = xpc_heartbeat_init_sn2;
        xpc_heartbeat_exit = xpc_heartbeat_exit_sn2;
        xpc_check_remote_hb = xpc_check_remote_hb_sn2;

        xpc_request_partition_activation = xpc_request_partition_activation_sn2;
        xpc_request_partition_reactivation =
            xpc_request_partition_reactivation_sn2;
        xpc_request_partition_deactivation =
            xpc_request_partition_deactivation_sn2;
        xpc_cancel_partition_deactivation_request =
            xpc_cancel_partition_deactivation_request_sn2;

        xpc_process_activate_IRQ_rcvd = xpc_process_activate_IRQ_rcvd_sn2;
        xpc_setup_infrastructure = xpc_setup_infrastructure_sn2;
        xpc_teardown_infrastructure = xpc_teardown_infrastructure_sn2;
        xpc_make_first_contact = xpc_make_first_contact_sn2;
        xpc_get_IPI_flags = xpc_get_IPI_flags_sn2;
        xpc_notify_senders_of_disconnect = xpc_notify_senders_of_disconnect_sn2;
        xpc_process_msg_IPI = xpc_process_msg_IPI_sn2;
        xpc_n_of_deliverable_msgs = xpc_n_of_deliverable_msgs_sn2;
        xpc_get_deliverable_msg = xpc_get_deliverable_msg_sn2;

        xpc_indicate_partition_engaged = xpc_indicate_partition_engaged_sn2;
        xpc_partition_engaged = xpc_partition_engaged_sn2;
        xpc_any_partition_engaged = xpc_any_partition_engaged_sn2;
        xpc_indicate_partition_disengaged =
            xpc_indicate_partition_disengaged_sn2;
        xpc_assume_partition_disengaged = xpc_assume_partition_disengaged_sn2;

        xpc_send_channel_closerequest = xpc_send_channel_closerequest_sn2;
        xpc_send_channel_closereply = xpc_send_channel_closereply_sn2;
        xpc_send_channel_openrequest = xpc_send_channel_openrequest_sn2;
        xpc_send_channel_openreply = xpc_send_channel_openreply_sn2;

        xpc_send_msg = xpc_send_msg_sn2;
        xpc_received_msg = xpc_received_msg_sn2;

        /* open up protections for IPI and [potentially] AMO operations */
        xpc_allow_IPI_ops_sn2();
        xpc_allow_AMO_ops_shub_wars_1_1_sn2();

        /*
         * This is safe to do before the xpc_hb_checker thread has started
         * because the handler releases a wait queue.  If an interrupt is
         * received before the thread is waiting, it will not go to sleep,
         * but rather immediately process the interrupt.
         */
        ret = request_irq(SGI_XPC_ACTIVATE, xpc_handle_activate_IRQ_sn2, 0,
                          "xpc hb", NULL);
        if (ret != 0) {
                dev_err(xpc_part, "can't register ACTIVATE IRQ handler, "
                        "errno=%d\n", -ret);
                xpc_disallow_IPI_ops_sn2();
        }
        return ret;
}

void
xpc_exit_sn2(void)
{
        free_irq(SGI_XPC_ACTIVATE, NULL);
        xpc_disallow_IPI_ops_sn2();
}