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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)
Tim Hockinbd784322007-07-21 17:10:37 +020017 0: always panic on uncorrected errors, log corrected errors
18 1: panic or SIGBUS on uncorrected errors, log corrected errors
19 2: SIGBUS or log uncorrected errors, log corrected errors
20 3: never panic or SIGBUS, log all errors (for testing only)
21 Default is 1
Andi Kleen8c566ef2005-09-12 18:49:24 +020022 Can be also set using sysfs which is preferable.
Linus Torvalds1da177e2005-04-16 15:20:36 -070023
24 nomce (for compatibility with i386): same as mce=off
25
26 Everything else is in sysfs now.
27
28APICs
29
30 apic Use IO-APIC. Default
31
32 noapic Don't use the IO-APIC.
33
34 disableapic Don't use the local APIC
35
36 nolapic Don't use the local APIC (alias for i386 compatibility)
37
38 pirq=... See Documentation/i386/IO-APIC.txt
39
40 noapictimer Don't set up the APIC timer
41
Andi Kleen14d98ca2005-05-20 14:27:59 -070042 no_timer_check Don't check the IO-APIC timer. This can work around
43 problems with incorrect timer initialization on some boards.
44
Andi Kleen73dea472006-02-03 21:50:50 +010045 apicmaintimer Run time keeping from the local APIC timer instead
46 of using the PIT/HPET interrupt for this. This is useful
47 when the PIT/HPET interrupts are unreliable.
48
49 noapicmaintimer Don't do time keeping using the APIC timer.
50 Useful when this option was auto selected, but doesn't work.
51
Andi Kleen0c3749c2006-02-03 21:51:41 +010052 apicpmtimer
53 Do APIC timer calibration using the pmtimer. Implies
54 apicmaintimer. Useful when your PIT timer is totally
55 broken.
56
Linus Torvaldsfea5f1e2007-01-08 15:04:46 -080057 disable_8254_timer / enable_8254_timer
58 Enable interrupt 0 timer routing over the 8254 in addition to over
59 the IO-APIC. The kernel tries to set a sensible default.
60
Linus Torvalds1da177e2005-04-16 15:20:36 -070061Early Console
62
63 syntax: earlyprintk=vga
64 earlyprintk=serial[,ttySn[,baudrate]]
65
66 The early console is useful when the kernel crashes before the
67 normal console is initialized. It is not enabled by
68 default because it has some cosmetic problems.
69 Append ,keep to not disable it when the real console takes over.
70 Only vga or serial at a time, not both.
71 Currently only ttyS0 and ttyS1 are supported.
72 Interaction with the standard serial driver is not very good.
73 The VGA output is eventually overwritten by the real console.
74
75Timing
76
77 notsc
78 Don't use the CPU time stamp counter to read the wall time.
79 This can be used to work around timing problems on multiprocessor systems
Andi Kleenef4d7cb2005-07-28 21:15:34 -070080 with not properly synchronized CPUs.
Linus Torvalds1da177e2005-04-16 15:20:36 -070081
82 report_lost_ticks
83 Report when timer interrupts are lost because some code turned off
84 interrupts for too long.
85
86 nmi_watchdog=NUMBER[,panic]
87 NUMBER can be:
88 0 don't use an NMI watchdog
89 1 use the IO-APIC timer for the NMI watchdog
90 2 use the local APIC for the NMI watchdog using a performance counter. Note
91 This will use one performance counter and the local APIC's performance
92 vector.
93 When panic is specified panic when an NMI watchdog timeout occurs.
94 This is useful when you use a panic=... timeout and need the box
95 quickly up again.
96
97 nohpet
98 Don't use the HPET timer.
99
100Idle loop
101
102 idle=poll
103 Don't do power saving in the idle loop using HLT, but poll for rescheduling
104 event. This will make the CPUs eat a lot more power, but may be useful
105 to get slightly better performance in multiprocessor benchmarks. It also
106 makes some profiling using performance counters more accurate.
Andi Kleenef4d7cb2005-07-28 21:15:34 -0700107 Please note that on systems with MONITOR/MWAIT support (like Intel EM64T
108 CPUs) this option has no performance advantage over the normal idle loop.
109 It may also interact badly with hyperthreading.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700110
111Rebooting
112
Huang, Ying9ad65e42008-01-30 13:31:19 +0100113 reboot=b[ios] | t[riple] | k[bd] | a[cpi] | e[fi] [, [w]arm | [c]old]
Matt LaPlanted6bc8ac2006-10-03 22:54:15 +0200114 bios Use the CPU reboot vector for warm reset
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115 warm Don't set the cold reboot flag
116 cold Set the cold reboot flag
117 triple Force a triple fault (init)
118 kbd Use the keyboard controller. cold reset (default)
Aaron Durbinfa20efd2008-01-30 13:31:17 +0100119 acpi Use the ACPI RESET_REG in the FADT. If ACPI is not configured or the
120 ACPI reset does not work, the reboot path attempts the reset using
121 the keyboard controller.
Huang, Ying9ad65e42008-01-30 13:31:19 +0100122 efi Use efi reset_system runtime service. If EFI is not configured or the
123 EFI reset does not work, the reboot path attempts the reset using
124 the keyboard controller.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700125
126 Using warm reset will be much faster especially on big memory
127 systems because the BIOS will not go through the memory check.
128 Disadvantage is that not all hardware will be completely reinitialized
129 on reboot so there may be boot problems on some systems.
130
131 reboot=force
132
133 Don't stop other CPUs on reboot. This can make reboot more reliable
134 in some cases.
135
136Non Executable Mappings
137
138 noexec=on|off
139
140 on Enable(default)
141 off Disable
142
143SMP
144
Andi Kleen420f8f62005-11-05 17:25:54 +0100145 additional_cpus=NUM Allow NUM more CPUs for hotplug
Andi Kleenf62a91f2006-01-11 22:42:35 +0100146 (defaults are specified by the BIOS, see Documentation/x86_64/cpu-hotplug-spec)
Andi Kleen420f8f62005-11-05 17:25:54 +0100147
Linus Torvalds1da177e2005-04-16 15:20:36 -0700148NUMA
149
150 numa=off Only set up a single NUMA node spanning all memory.
151
152 numa=noacpi Don't parse the SRAT table for NUMA setup
153
David Rientjes8b8ca80e2007-05-02 19:27:09 +0200154 numa=fake=CMDLINE
155 If a number, fakes CMDLINE nodes and ignores NUMA setup of the
156 actual machine. Otherwise, system memory is configured
157 depending on the sizes and coefficients listed. For example:
David Rientjes382591d2007-05-02 19:27:09 +0200158 numa=fake=2*512,1024,4*256,*128
159 gives two 512M nodes, a 1024M node, four 256M nodes, and the
160 rest split into 128M chunks. If the last character of CMDLINE
161 is a *, the remaining memory is divided up equally among its
162 coefficient:
163 numa=fake=2*512,2*
164 gives two 512M nodes and the rest split into two nodes.
165 Otherwise, the remaining system RAM is allocated to an
166 additional node.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700167
Andi Kleen68a3a7f2006-04-07 19:49:18 +0200168 numa=hotadd=percent
169 Only allow hotadd memory to preallocate page structures upto
170 percent of already available memory.
171 numa=hotadd=0 will disable hotadd memory.
172
Linus Torvalds1da177e2005-04-16 15:20:36 -0700173ACPI
174
175 acpi=off Don't enable ACPI
176 acpi=ht Use ACPI boot table parsing, but don't enable ACPI
177 interpreter
178 acpi=force Force ACPI on (currently not needed)
179
180 acpi=strict Disable out of spec ACPI workarounds.
181
182 acpi_sci={edge,level,high,low} Set up ACPI SCI interrupt.
183
184 acpi=noirq Don't route interrupts
185
186PCI
187
188 pci=off Don't use PCI
189 pci=conf1 Use conf1 access.
190 pci=conf2 Use conf2 access.
191 pci=rom Assign ROMs.
192 pci=assign-busses Assign busses
193 pci=irqmask=MASK Set PCI interrupt mask to MASK
194 pci=lastbus=NUMBER Scan upto NUMBER busses, no matter what the mptable says.
195 pci=noacpi Don't use ACPI to set up PCI interrupt routing.
196
Karsten Weiss55588702007-02-13 13:26:21 +0100197IOMMU (input/output memory management unit)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700198
Karsten Weiss55588702007-02-13 13:26:21 +0100199 Currently four x86-64 PCI-DMA mapping implementations exist:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700200
Karsten Weiss55588702007-02-13 13:26:21 +0100201 1. <arch/x86_64/kernel/pci-nommu.c>: use no hardware/software IOMMU at all
202 (e.g. because you have < 3 GB memory).
203 Kernel boot message: "PCI-DMA: Disabling IOMMU"
Linus Torvalds1da177e2005-04-16 15:20:36 -0700204
Karsten Weiss55588702007-02-13 13:26:21 +0100205 2. <arch/x86_64/kernel/pci-gart.c>: AMD GART based hardware IOMMU.
206 Kernel boot message: "PCI-DMA: using GART IOMMU"
Linus Torvalds1da177e2005-04-16 15:20:36 -0700207
Karsten Weiss55588702007-02-13 13:26:21 +0100208 3. <arch/x86_64/kernel/pci-swiotlb.c> : Software IOMMU implementation. Used
209 e.g. if there is no hardware IOMMU in the system and it is need because
210 you have >3GB memory or told the kernel to us it (iommu=soft))
211 Kernel boot message: "PCI-DMA: Using software bounce buffering
212 for IO (SWIOTLB)"
213
214 4. <arch/x86_64/pci-calgary.c> : IBM Calgary hardware IOMMU. Used in IBM
215 pSeries and xSeries servers. This hardware IOMMU supports DMA address
216 mapping with memory protection, etc.
217 Kernel boot message: "PCI-DMA: Using Calgary IOMMU"
218
219 iommu=[<size>][,noagp][,off][,force][,noforce][,leak[=<nr_of_leak_pages>]
220 [,memaper[=<order>]][,merge][,forcesac][,fullflush][,nomerge]
221 [,noaperture][,calgary]
222
223 General iommu options:
224 off Don't initialize and use any kind of IOMMU.
225 noforce Don't force hardware IOMMU usage when it is not needed.
226 (default).
227 force Force the use of the hardware IOMMU even when it is
228 not actually needed (e.g. because < 3 GB memory).
229 soft Use software bounce buffering (SWIOTLB) (default for
230 Intel machines). This can be used to prevent the usage
231 of an available hardware IOMMU.
232
233 iommu options only relevant to the AMD GART hardware IOMMU:
234 <size> Set the size of the remapping area in bytes.
235 allowed Overwrite iommu off workarounds for specific chipsets.
236 fullflush Flush IOMMU on each allocation (default).
237 nofullflush Don't use IOMMU fullflush.
238 leak Turn on simple iommu leak tracing (only when
239 CONFIG_IOMMU_LEAK is on). Default number of leak pages
240 is 20.
241 memaper[=<order>] Allocate an own aperture over RAM with size 32MB<<order.
242 (default: order=1, i.e. 64MB)
Randy Dunlap57d30772007-02-13 13:26:23 +0100243 merge Do scatter-gather (SG) merging. Implies "force"
Karsten Weiss55588702007-02-13 13:26:21 +0100244 (experimental).
Randy Dunlap57d30772007-02-13 13:26:23 +0100245 nomerge Don't do scatter-gather (SG) merging.
Karsten Weiss55588702007-02-13 13:26:21 +0100246 noaperture Ask the IOMMU not to touch the aperture for AGP.
247 forcesac Force single-address cycle (SAC) mode for masks <40bits
248 (experimental).
249 noagp Don't initialize the AGP driver and use full aperture.
250 allowdac Allow double-address cycle (DAC) mode, i.e. DMA >4GB.
251 DAC is used with 32-bit PCI to push a 64-bit address in
252 two cycles. When off all DMA over >4GB is forced through
253 an IOMMU or software bounce buffering.
254 nodac Forbid DAC mode, i.e. DMA >4GB.
255 panic Always panic when IOMMU overflows.
256 calgary Use the Calgary IOMMU if it is available
257
258 iommu options only relevant to the software bounce buffering (SWIOTLB) IOMMU
259 implementation:
260 swiotlb=<pages>[,force]
261 <pages> Prereserve that many 128K pages for the software IO
262 bounce buffering.
263 force Force all IO through the software TLB.
264
265 Settings for the IBM Calgary hardware IOMMU currently found in IBM
266 pSeries and xSeries machines:
267
268 calgary=[64k,128k,256k,512k,1M,2M,4M,8M]
269 calgary=[translate_empty_slots]
270 calgary=[disable=<PCI bus number>]
271 panic Always panic when IOMMU overflows
Jon Masone4650582006-06-26 13:58:14 +0200272
273 64k,...,8M - Set the size of each PCI slot's translation table
274 when using the Calgary IOMMU. This is the size of the translation
275 table itself in main memory. The smallest table, 64k, covers an IO
276 space of 32MB; the largest, 8MB table, can cover an IO space of
277 4GB. Normally the kernel will make the right choice by itself.
278
279 translate_empty_slots - Enable translation even on slots that have
280 no devices attached to them, in case a device will be hotplugged
281 in the future.
282
283 disable=<PCI bus number> - Disable translation on a given PHB. For
284 example, the built-in graphics adapter resides on the first bridge
285 (PCI bus number 0); if translation (isolation) is enabled on this
286 bridge, X servers that access the hardware directly from user
287 space might stop working. Use this option if you have devices that
288 are accessed from userspace directly on some PCI host bridge.
289
Linus Torvalds1da177e2005-04-16 15:20:36 -0700290Debugging
291
Randy Dunlap57d30772007-02-13 13:26:23 +0100292 oops=panic Always panic on oopses. Default is to just kill the process,
293 but there is a small probability of deadlocking the machine.
294 This will also cause panics on machine check exceptions.
295 Useful together with panic=30 to trigger a reboot.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700296
Randy Dunlap57d30772007-02-13 13:26:23 +0100297 kstack=N Print N words from the kernel stack in oops dumps.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700298
Randy Dunlap57d30772007-02-13 13:26:23 +0100299 pagefaulttrace Dump all page faults. Only useful for extreme debugging
Andi Kleen9e43e1b2005-11-05 17:25:54 +0100300 and will create a lot of output.
301
Andi Kleenb783fd92006-07-28 14:44:54 +0200302 call_trace=[old|both|newfallback|new]
303 old: use old inexact backtracer
304 new: use new exact dwarf2 unwinder
305 both: print entries from both
306 newfallback: use new unwinder but fall back to old if it gets
307 stuck (default)
308
Huang, Ying9ad65e42008-01-30 13:31:19 +0100309EFI
310
311 noefi Disable EFI support
312
Randy Dunlap57d30772007-02-13 13:26:23 +0100313Miscellaneous