Linux 2.6.31-rc6
[linux-2.6] / arch / x86 / xen / irq.c
1 #include <linux/hardirq.h>
2
3 #include <xen/interface/xen.h>
4 #include <xen/interface/sched.h>
5 #include <xen/interface/vcpu.h>
6
7 #include <asm/xen/hypercall.h>
8 #include <asm/xen/hypervisor.h>
9
10 #include "xen-ops.h"
11
12 /*
13  * Force a proper event-channel callback from Xen after clearing the
14  * callback mask. We do this in a very simple manner, by making a call
15  * down into Xen. The pending flag will be checked by Xen on return.
16  */
17 void xen_force_evtchn_callback(void)
18 {
19         (void)HYPERVISOR_xen_version(0, NULL);
20 }
21
22 static unsigned long xen_save_fl(void)
23 {
24         struct vcpu_info *vcpu;
25         unsigned long flags;
26
27         vcpu = percpu_read(xen_vcpu);
28
29         /* flag has opposite sense of mask */
30         flags = !vcpu->evtchn_upcall_mask;
31
32         /* convert to IF type flag
33            -0 -> 0x00000000
34            -1 -> 0xffffffff
35         */
36         return (-flags) & X86_EFLAGS_IF;
37 }
38 PV_CALLEE_SAVE_REGS_THUNK(xen_save_fl);
39
40 static void xen_restore_fl(unsigned long flags)
41 {
42         struct vcpu_info *vcpu;
43
44         /* convert from IF type flag */
45         flags = !(flags & X86_EFLAGS_IF);
46
47         /* There's a one instruction preempt window here.  We need to
48            make sure we're don't switch CPUs between getting the vcpu
49            pointer and updating the mask. */
50         preempt_disable();
51         vcpu = percpu_read(xen_vcpu);
52         vcpu->evtchn_upcall_mask = flags;
53         preempt_enable_no_resched();
54
55         /* Doesn't matter if we get preempted here, because any
56            pending event will get dealt with anyway. */
57
58         if (flags == 0) {
59                 preempt_check_resched();
60                 barrier(); /* unmask then check (avoid races) */
61                 if (unlikely(vcpu->evtchn_upcall_pending))
62                         xen_force_evtchn_callback();
63         }
64 }
65 PV_CALLEE_SAVE_REGS_THUNK(xen_restore_fl);
66
67 static void xen_irq_disable(void)
68 {
69         /* There's a one instruction preempt window here.  We need to
70            make sure we're don't switch CPUs between getting the vcpu
71            pointer and updating the mask. */
72         preempt_disable();
73         percpu_read(xen_vcpu)->evtchn_upcall_mask = 1;
74         preempt_enable_no_resched();
75 }
76 PV_CALLEE_SAVE_REGS_THUNK(xen_irq_disable);
77
78 static void xen_irq_enable(void)
79 {
80         struct vcpu_info *vcpu;
81
82         /* We don't need to worry about being preempted here, since
83            either a) interrupts are disabled, so no preemption, or b)
84            the caller is confused and is trying to re-enable interrupts
85            on an indeterminate processor. */
86
87         vcpu = percpu_read(xen_vcpu);
88         vcpu->evtchn_upcall_mask = 0;
89
90         /* Doesn't matter if we get preempted here, because any
91            pending event will get dealt with anyway. */
92
93         barrier(); /* unmask then check (avoid races) */
94         if (unlikely(vcpu->evtchn_upcall_pending))
95                 xen_force_evtchn_callback();
96 }
97 PV_CALLEE_SAVE_REGS_THUNK(xen_irq_enable);
98
99 static void xen_safe_halt(void)
100 {
101         /* Blocking includes an implicit local_irq_enable(). */
102         if (HYPERVISOR_sched_op(SCHEDOP_block, NULL) != 0)
103                 BUG();
104 }
105
106 static void xen_halt(void)
107 {
108         if (irqs_disabled())
109                 HYPERVISOR_vcpu_op(VCPUOP_down, smp_processor_id(), NULL);
110         else
111                 xen_safe_halt();
112 }
113
114 static const struct pv_irq_ops xen_irq_ops __initdata = {
115         .init_IRQ = xen_init_IRQ,
116
117         .save_fl = PV_CALLEE_SAVE(xen_save_fl),
118         .restore_fl = PV_CALLEE_SAVE(xen_restore_fl),
119         .irq_disable = PV_CALLEE_SAVE(xen_irq_disable),
120         .irq_enable = PV_CALLEE_SAVE(xen_irq_enable),
121
122         .safe_halt = xen_safe_halt,
123         .halt = xen_halt,
124 #ifdef CONFIG_X86_64
125         .adjust_exception_frame = xen_adjust_exception_frame,
126 #endif
127 };
128
129 void __init xen_init_irq_ops()
130 {
131         pv_irq_ops = xen_irq_ops;
132 }