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Linus Torvalds1da177e2005-04-16 15:20:36 -07001AMD64 specific boot options
2
3There are many others (usually documented in driver documentation), but
4only the AMD64 specific ones are listed here.
5
6Machine check
7
8 mce=off disable machine check
Andi Kleend5172f22005-08-07 09:42:07 -07009 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
13 in a reboot.
Andi Kleen8c566ef2005-09-12 18:49:24 +020014 mce=tolerancelevel (number)
15 0: always panic, 1: panic if deadlock possible,
16 2: try to avoid panic, 3: never panic or exit (for testing)
17 default is 1
18 Can be also set using sysfs which is preferable.
Linus Torvalds1da177e2005-04-16 15:20:36 -070019
20 nomce (for compatibility with i386): same as mce=off
21
22 Everything else is in sysfs now.
23
24APICs
25
26 apic Use IO-APIC. Default
27
28 noapic Don't use the IO-APIC.
29
30 disableapic Don't use the local APIC
31
32 nolapic Don't use the local APIC (alias for i386 compatibility)
33
34 pirq=... See Documentation/i386/IO-APIC.txt
35
36 noapictimer Don't set up the APIC timer
37
Andi Kleen14d98ca2005-05-20 14:27:59 -070038 no_timer_check Don't check the IO-APIC timer. This can work around
39 problems with incorrect timer initialization on some boards.
40
Linus Torvalds1da177e2005-04-16 15:20:36 -070041Early Console
42
43 syntax: earlyprintk=vga
44 earlyprintk=serial[,ttySn[,baudrate]]
45
46 The early console is useful when the kernel crashes before the
47 normal console is initialized. It is not enabled by
48 default because it has some cosmetic problems.
49 Append ,keep to not disable it when the real console takes over.
50 Only vga or serial at a time, not both.
51 Currently only ttyS0 and ttyS1 are supported.
52 Interaction with the standard serial driver is not very good.
53 The VGA output is eventually overwritten by the real console.
54
55Timing
56
57 notsc
58 Don't use the CPU time stamp counter to read the wall time.
59 This can be used to work around timing problems on multiprocessor systems
Andi Kleenef4d7cb2005-07-28 21:15:34 -070060 with not properly synchronized CPUs.
Linus Torvalds1da177e2005-04-16 15:20:36 -070061
62 report_lost_ticks
63 Report when timer interrupts are lost because some code turned off
64 interrupts for too long.
65
66 nmi_watchdog=NUMBER[,panic]
67 NUMBER can be:
68 0 don't use an NMI watchdog
69 1 use the IO-APIC timer for the NMI watchdog
70 2 use the local APIC for the NMI watchdog using a performance counter. Note
71 This will use one performance counter and the local APIC's performance
72 vector.
73 When panic is specified panic when an NMI watchdog timeout occurs.
74 This is useful when you use a panic=... timeout and need the box
75 quickly up again.
76
77 nohpet
78 Don't use the HPET timer.
79
80Idle loop
81
82 idle=poll
83 Don't do power saving in the idle loop using HLT, but poll for rescheduling
84 event. This will make the CPUs eat a lot more power, but may be useful
85 to get slightly better performance in multiprocessor benchmarks. It also
86 makes some profiling using performance counters more accurate.
Andi Kleenef4d7cb2005-07-28 21:15:34 -070087 Please note that on systems with MONITOR/MWAIT support (like Intel EM64T
88 CPUs) this option has no performance advantage over the normal idle loop.
89 It may also interact badly with hyperthreading.
Linus Torvalds1da177e2005-04-16 15:20:36 -070090
91Rebooting
92
93 reboot=b[ios] | t[riple] | k[bd] [, [w]arm | [c]old]
94 bios Use the CPU reboto vector for warm reset
95 warm Don't set the cold reboot flag
96 cold Set the cold reboot flag
97 triple Force a triple fault (init)
98 kbd Use the keyboard controller. cold reset (default)
99
100 Using warm reset will be much faster especially on big memory
101 systems because the BIOS will not go through the memory check.
102 Disadvantage is that not all hardware will be completely reinitialized
103 on reboot so there may be boot problems on some systems.
104
105 reboot=force
106
107 Don't stop other CPUs on reboot. This can make reboot more reliable
108 in some cases.
109
110Non Executable Mappings
111
112 noexec=on|off
113
114 on Enable(default)
115 off Disable
116
117SMP
118
119 nosmp Only use a single CPU
120
121 maxcpus=NUMBER only use upto NUMBER CPUs
122
123 cpumask=MASK only use cpus with bits set in mask
124
125NUMA
126
127 numa=off Only set up a single NUMA node spanning all memory.
128
129 numa=noacpi Don't parse the SRAT table for NUMA setup
130
131 numa=fake=X Fake X nodes and ignore NUMA setup of the actual machine.
132
133ACPI
134
135 acpi=off Don't enable ACPI
136 acpi=ht Use ACPI boot table parsing, but don't enable ACPI
137 interpreter
138 acpi=force Force ACPI on (currently not needed)
139
140 acpi=strict Disable out of spec ACPI workarounds.
141
142 acpi_sci={edge,level,high,low} Set up ACPI SCI interrupt.
143
144 acpi=noirq Don't route interrupts
145
146PCI
147
148 pci=off Don't use PCI
149 pci=conf1 Use conf1 access.
150 pci=conf2 Use conf2 access.
151 pci=rom Assign ROMs.
152 pci=assign-busses Assign busses
153 pci=irqmask=MASK Set PCI interrupt mask to MASK
154 pci=lastbus=NUMBER Scan upto NUMBER busses, no matter what the mptable says.
155 pci=noacpi Don't use ACPI to set up PCI interrupt routing.
156
157IOMMU
158
159 iommu=[size][,noagp][,off][,force][,noforce][,leak][,memaper[=order]][,merge]
160 [,forcesac][,fullflush][,nomerge][,noaperture]
161 size set size of iommu (in bytes)
162 noagp don't initialize the AGP driver and use full aperture.
163 off don't use the IOMMU
164 leak turn on simple iommu leak tracing (only when CONFIG_IOMMU_LEAK is on)
165 memaper[=order] allocate an own aperture over RAM with size 32MB^order.
166 noforce don't force IOMMU usage. Default.
167 force Force IOMMU.
168 merge Do SG merging. Implies force (experimental)
169 nomerge Don't do SG merging.
170 forcesac For SAC mode for masks <40bits (experimental)
171 fullflush Flush IOMMU on each allocation (default)
172 nofullflush Don't use IOMMU fullflush
173 allowed overwrite iommu off workarounds for specific chipsets.
174 soft Use software bounce buffering (default for Intel machines)
175 noaperture Don't touch the aperture for AGP.
176
177 swiotlb=pages[,force]
178
179 pages Prereserve that many 128K pages for the software IO bounce buffering.
180 force Force all IO through the software TLB.
181
182Debugging
183
184 oops=panic Always panic on oopses. Default is to just kill the process,
185 but there is a small probability of deadlocking the machine.
186 This will also cause panics on machine check exceptions.
187 Useful together with panic=30 to trigger a reboot.
188
189 kstack=N Print that many words from the kernel stack in oops dumps.
190
191Misc
192
193 noreplacement Don't replace instructions with more appropiate ones
Andi Kleenef4d7cb2005-07-28 21:15:34 -0700194 for the CPU. This may be useful on asymmetric MP systems
195 where some CPU have less capabilities than the others.