1 AMD64 specific boot options
3 There are many others (usually documented in driver documentation), but
4 only the AMD64 specific ones are listed here.
8 mce=off disable machine check
9 mce=bootlog Enable logging of machine checks left over from booting.
10 Disabled by default because some BIOS leave bogus ones.
11 If your BIOS doesn't do that it's a good idea to enable though
12 to make sure you log even machine check events that result
15 nomce (for compatibility with i386): same as mce=off
17 Everything else is in sysfs now.
21 apic Use IO-APIC. Default
23 noapic Don't use the IO-APIC.
25 disableapic Don't use the local APIC
27 nolapic Don't use the local APIC (alias for i386 compatibility)
29 pirq=... See Documentation/i386/IO-APIC.txt
31 noapictimer Don't set up the APIC timer
33 no_timer_check Don't check the IO-APIC timer. This can work around
34 problems with incorrect timer initialization on some boards.
38 syntax: earlyprintk=vga
39 earlyprintk=serial[,ttySn[,baudrate]]
41 The early console is useful when the kernel crashes before the
42 normal console is initialized. It is not enabled by
43 default because it has some cosmetic problems.
44 Append ,keep to not disable it when the real console takes over.
45 Only vga or serial at a time, not both.
46 Currently only ttyS0 and ttyS1 are supported.
47 Interaction with the standard serial driver is not very good.
48 The VGA output is eventually overwritten by the real console.
53 Don't use the CPU time stamp counter to read the wall time.
54 This can be used to work around timing problems on multiprocessor systems
55 with not properly synchronized CPUs.
58 Report when timer interrupts are lost because some code turned off
59 interrupts for too long.
61 nmi_watchdog=NUMBER[,panic]
63 0 don't use an NMI watchdog
64 1 use the IO-APIC timer for the NMI watchdog
65 2 use the local APIC for the NMI watchdog using a performance counter. Note
66 This will use one performance counter and the local APIC's performance
68 When panic is specified panic when an NMI watchdog timeout occurs.
69 This is useful when you use a panic=... timeout and need the box
73 Don't use the HPET timer.
78 Don't do power saving in the idle loop using HLT, but poll for rescheduling
79 event. This will make the CPUs eat a lot more power, but may be useful
80 to get slightly better performance in multiprocessor benchmarks. It also
81 makes some profiling using performance counters more accurate.
82 Please note that on systems with MONITOR/MWAIT support (like Intel EM64T
83 CPUs) this option has no performance advantage over the normal idle loop.
84 It may also interact badly with hyperthreading.
88 reboot=b[ios] | t[riple] | k[bd] [, [w]arm | [c]old]
89 bios Use the CPU reboto vector for warm reset
90 warm Don't set the cold reboot flag
91 cold Set the cold reboot flag
92 triple Force a triple fault (init)
93 kbd Use the keyboard controller. cold reset (default)
95 Using warm reset will be much faster especially on big memory
96 systems because the BIOS will not go through the memory check.
97 Disadvantage is that not all hardware will be completely reinitialized
98 on reboot so there may be boot problems on some systems.
102 Don't stop other CPUs on reboot. This can make reboot more reliable
105 Non Executable Mappings
114 nosmp Only use a single CPU
116 maxcpus=NUMBER only use upto NUMBER CPUs
118 cpumask=MASK only use cpus with bits set in mask
122 numa=off Only set up a single NUMA node spanning all memory.
124 numa=noacpi Don't parse the SRAT table for NUMA setup
126 numa=fake=X Fake X nodes and ignore NUMA setup of the actual machine.
130 acpi=off Don't enable ACPI
131 acpi=ht Use ACPI boot table parsing, but don't enable ACPI
133 acpi=force Force ACPI on (currently not needed)
135 acpi=strict Disable out of spec ACPI workarounds.
137 acpi_sci={edge,level,high,low} Set up ACPI SCI interrupt.
139 acpi=noirq Don't route interrupts
143 pci=off Don't use PCI
144 pci=conf1 Use conf1 access.
145 pci=conf2 Use conf2 access.
147 pci=assign-busses Assign busses
148 pci=irqmask=MASK Set PCI interrupt mask to MASK
149 pci=lastbus=NUMBER Scan upto NUMBER busses, no matter what the mptable says.
150 pci=noacpi Don't use ACPI to set up PCI interrupt routing.
154 iommu=[size][,noagp][,off][,force][,noforce][,leak][,memaper[=order]][,merge]
155 [,forcesac][,fullflush][,nomerge][,noaperture]
156 size set size of iommu (in bytes)
157 noagp don't initialize the AGP driver and use full aperture.
158 off don't use the IOMMU
159 leak turn on simple iommu leak tracing (only when CONFIG_IOMMU_LEAK is on)
160 memaper[=order] allocate an own aperture over RAM with size 32MB^order.
161 noforce don't force IOMMU usage. Default.
163 merge Do SG merging. Implies force (experimental)
164 nomerge Don't do SG merging.
165 forcesac For SAC mode for masks <40bits (experimental)
166 fullflush Flush IOMMU on each allocation (default)
167 nofullflush Don't use IOMMU fullflush
168 allowed overwrite iommu off workarounds for specific chipsets.
169 soft Use software bounce buffering (default for Intel machines)
170 noaperture Don't touch the aperture for AGP.
172 swiotlb=pages[,force]
174 pages Prereserve that many 128K pages for the software IO bounce buffering.
175 force Force all IO through the software TLB.
179 oops=panic Always panic on oopses. Default is to just kill the process,
180 but there is a small probability of deadlocking the machine.
181 This will also cause panics on machine check exceptions.
182 Useful together with panic=30 to trigger a reboot.
184 kstack=N Print that many words from the kernel stack in oops dumps.
188 noreplacement Don't replace instructions with more appropiate ones
189 for the CPU. This may be useful on asymmetric MP systems
190 where some CPU have less capabilities than the others.