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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.
Andi Kleene5835382005-11-05 17:25:54 +010010 Disabled by default on AMD because some BIOS leave bogus ones.
Andi Kleend5172f22005-08-07 09:42:07 -070011 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
Andi Kleene5835382005-11-05 17:25:54 +010013 in a reboot. On Intel systems it is enabled by default.
14 mce=nobootlog
15 Disable boot machine check logging.
Andi Kleen8c566ef2005-09-12 18:49:24 +020016 mce=tolerancelevel (number)
17 0: always panic, 1: panic if deadlock possible,
18 2: try to avoid panic, 3: never panic or exit (for testing)
19 default is 1
20 Can be also set using sysfs which is preferable.
Linus Torvalds1da177e2005-04-16 15:20:36 -070021
22 nomce (for compatibility with i386): same as mce=off
23
24 Everything else is in sysfs now.
25
26APICs
27
28 apic Use IO-APIC. Default
29
30 noapic Don't use the IO-APIC.
31
32 disableapic Don't use the local APIC
33
34 nolapic Don't use the local APIC (alias for i386 compatibility)
35
36 pirq=... See Documentation/i386/IO-APIC.txt
37
38 noapictimer Don't set up the APIC timer
39
Andi Kleen14d98ca2005-05-20 14:27:59 -070040 no_timer_check Don't check the IO-APIC timer. This can work around
41 problems with incorrect timer initialization on some boards.
42
Andi Kleen73dea472006-02-03 21:50:50 +010043 apicmaintimer Run time keeping from the local APIC timer instead
44 of using the PIT/HPET interrupt for this. This is useful
45 when the PIT/HPET interrupts are unreliable.
46
47 noapicmaintimer Don't do time keeping using the APIC timer.
48 Useful when this option was auto selected, but doesn't work.
49
Andi Kleen0c3749c2006-02-03 21:51:41 +010050 apicpmtimer
51 Do APIC timer calibration using the pmtimer. Implies
52 apicmaintimer. Useful when your PIT timer is totally
53 broken.
54
Andi Kleenab9b32e2006-02-26 04:18:52 +010055 disable_8254_timer / enable_8254_timer
56 Enable interrupt 0 timer routing over the 8254 in addition to over
57 the IO-APIC. The kernel tries to set a sensible default.
58
Linus Torvalds1da177e2005-04-16 15:20:36 -070059Early Console
60
61 syntax: earlyprintk=vga
62 earlyprintk=serial[,ttySn[,baudrate]]
63
64 The early console is useful when the kernel crashes before the
65 normal console is initialized. It is not enabled by
66 default because it has some cosmetic problems.
67 Append ,keep to not disable it when the real console takes over.
68 Only vga or serial at a time, not both.
69 Currently only ttyS0 and ttyS1 are supported.
70 Interaction with the standard serial driver is not very good.
71 The VGA output is eventually overwritten by the real console.
72
73Timing
74
75 notsc
76 Don't use the CPU time stamp counter to read the wall time.
77 This can be used to work around timing problems on multiprocessor systems
Andi Kleenef4d7cb2005-07-28 21:15:34 -070078 with not properly synchronized CPUs.
Linus Torvalds1da177e2005-04-16 15:20:36 -070079
80 report_lost_ticks
81 Report when timer interrupts are lost because some code turned off
82 interrupts for too long.
83
84 nmi_watchdog=NUMBER[,panic]
85 NUMBER can be:
86 0 don't use an NMI watchdog
87 1 use the IO-APIC timer for the NMI watchdog
88 2 use the local APIC for the NMI watchdog using a performance counter. Note
89 This will use one performance counter and the local APIC's performance
90 vector.
91 When panic is specified panic when an NMI watchdog timeout occurs.
92 This is useful when you use a panic=... timeout and need the box
93 quickly up again.
94
95 nohpet
96 Don't use the HPET timer.
97
98Idle loop
99
100 idle=poll
101 Don't do power saving in the idle loop using HLT, but poll for rescheduling
102 event. This will make the CPUs eat a lot more power, but may be useful
103 to get slightly better performance in multiprocessor benchmarks. It also
104 makes some profiling using performance counters more accurate.
Andi Kleenef4d7cb2005-07-28 21:15:34 -0700105 Please note that on systems with MONITOR/MWAIT support (like Intel EM64T
106 CPUs) this option has no performance advantage over the normal idle loop.
107 It may also interact badly with hyperthreading.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700108
109Rebooting
110
111 reboot=b[ios] | t[riple] | k[bd] [, [w]arm | [c]old]
112 bios Use the CPU reboto vector for warm reset
113 warm Don't set the cold reboot flag
114 cold Set the cold reboot flag
115 triple Force a triple fault (init)
116 kbd Use the keyboard controller. cold reset (default)
117
118 Using warm reset will be much faster especially on big memory
119 systems because the BIOS will not go through the memory check.
120 Disadvantage is that not all hardware will be completely reinitialized
121 on reboot so there may be boot problems on some systems.
122
123 reboot=force
124
125 Don't stop other CPUs on reboot. This can make reboot more reliable
126 in some cases.
127
128Non Executable Mappings
129
130 noexec=on|off
131
132 on Enable(default)
133 off Disable
134
135SMP
136
137 nosmp Only use a single CPU
138
139 maxcpus=NUMBER only use upto NUMBER CPUs
140
141 cpumask=MASK only use cpus with bits set in mask
142
Andi Kleen420f8f62005-11-05 17:25:54 +0100143 additional_cpus=NUM Allow NUM more CPUs for hotplug
Andi Kleenf62a91f2006-01-11 22:42:35 +0100144 (defaults are specified by the BIOS, see Documentation/x86_64/cpu-hotplug-spec)
Andi Kleen420f8f62005-11-05 17:25:54 +0100145
Linus Torvalds1da177e2005-04-16 15:20:36 -0700146NUMA
147
148 numa=off Only set up a single NUMA node spanning all memory.
149
150 numa=noacpi Don't parse the SRAT table for NUMA setup
151
152 numa=fake=X Fake X nodes and ignore NUMA setup of the actual machine.
153
Andi Kleen68a3a7f2006-04-07 19:49:18 +0200154 numa=hotadd=percent
155 Only allow hotadd memory to preallocate page structures upto
156 percent of already available memory.
157 numa=hotadd=0 will disable hotadd memory.
158
Linus Torvalds1da177e2005-04-16 15:20:36 -0700159ACPI
160
161 acpi=off Don't enable ACPI
162 acpi=ht Use ACPI boot table parsing, but don't enable ACPI
163 interpreter
164 acpi=force Force ACPI on (currently not needed)
165
166 acpi=strict Disable out of spec ACPI workarounds.
167
168 acpi_sci={edge,level,high,low} Set up ACPI SCI interrupt.
169
170 acpi=noirq Don't route interrupts
171
172PCI
173
174 pci=off Don't use PCI
175 pci=conf1 Use conf1 access.
176 pci=conf2 Use conf2 access.
177 pci=rom Assign ROMs.
178 pci=assign-busses Assign busses
179 pci=irqmask=MASK Set PCI interrupt mask to MASK
180 pci=lastbus=NUMBER Scan upto NUMBER busses, no matter what the mptable says.
181 pci=noacpi Don't use ACPI to set up PCI interrupt routing.
182
183IOMMU
184
185 iommu=[size][,noagp][,off][,force][,noforce][,leak][,memaper[=order]][,merge]
186 [,forcesac][,fullflush][,nomerge][,noaperture]
187 size set size of iommu (in bytes)
188 noagp don't initialize the AGP driver and use full aperture.
189 off don't use the IOMMU
190 leak turn on simple iommu leak tracing (only when CONFIG_IOMMU_LEAK is on)
191 memaper[=order] allocate an own aperture over RAM with size 32MB^order.
192 noforce don't force IOMMU usage. Default.
193 force Force IOMMU.
194 merge Do SG merging. Implies force (experimental)
195 nomerge Don't do SG merging.
196 forcesac For SAC mode for masks <40bits (experimental)
197 fullflush Flush IOMMU on each allocation (default)
198 nofullflush Don't use IOMMU fullflush
199 allowed overwrite iommu off workarounds for specific chipsets.
200 soft Use software bounce buffering (default for Intel machines)
201 noaperture Don't touch the aperture for AGP.
202
203 swiotlb=pages[,force]
204
205 pages Prereserve that many 128K pages for the software IO bounce buffering.
206 force Force all IO through the software TLB.
207
Jon Masone4650582006-06-26 13:58:14 +0200208 calgary=[64k,128k,256k,512k,1M,2M,4M,8M]
209 calgary=[translate_empty_slots]
210 calgary=[disable=<PCI bus number>]
211
212 64k,...,8M - Set the size of each PCI slot's translation table
213 when using the Calgary IOMMU. This is the size of the translation
214 table itself in main memory. The smallest table, 64k, covers an IO
215 space of 32MB; the largest, 8MB table, can cover an IO space of
216 4GB. Normally the kernel will make the right choice by itself.
217
218 translate_empty_slots - Enable translation even on slots that have
219 no devices attached to them, in case a device will be hotplugged
220 in the future.
221
222 disable=<PCI bus number> - Disable translation on a given PHB. For
223 example, the built-in graphics adapter resides on the first bridge
224 (PCI bus number 0); if translation (isolation) is enabled on this
225 bridge, X servers that access the hardware directly from user
226 space might stop working. Use this option if you have devices that
227 are accessed from userspace directly on some PCI host bridge.
228
Linus Torvalds1da177e2005-04-16 15:20:36 -0700229Debugging
230
231 oops=panic Always panic on oopses. Default is to just kill the process,
232 but there is a small probability of deadlocking the machine.
233 This will also cause panics on machine check exceptions.
234 Useful together with panic=30 to trigger a reboot.
235
236 kstack=N Print that many words from the kernel stack in oops dumps.
237
Andi Kleen9e43e1b2005-11-05 17:25:54 +0100238 pagefaulttrace Dump all page faults. Only useful for extreme debugging
239 and will create a lot of output.
240
Andi Kleenb783fd92006-07-28 14:44:54 +0200241 call_trace=[old|both|newfallback|new]
242 old: use old inexact backtracer
243 new: use new exact dwarf2 unwinder
244 both: print entries from both
245 newfallback: use new unwinder but fall back to old if it gets
246 stuck (default)
247
Linus Torvalds1da177e2005-04-16 15:20:36 -0700248Misc
249
Adrian Bunk575c9682006-01-15 02:00:17 +0100250 noreplacement Don't replace instructions with more appropriate ones
Andi Kleenef4d7cb2005-07-28 21:15:34 -0700251 for the CPU. This may be useful on asymmetric MP systems
252 where some CPU have less capabilities than the others.