x86/x86_64/boot-options.rst

1 .. SPDX-License-Identifier: GPL-2.0
27 		This option will be useful if you have no interest in any
39 		Do not opt-in to Local MCE delivery. Use legacy method
43 		Disabled by default on AMD Fam10h and older because some BIOS
47 		in a reboot. On Intel systems it is enabled by default.
52 		Sets the time in us to wait for other CPUs on machine checks. 0
55 		Don't overwrite the bios-set CMCI threshold. This boot option
62 		Force-enable recoverable machine check code paths
73 	Use IO-APIC. Default
76 	Don't use the IO-APIC.
85 	See Documentation/arch/x86/i386/IO-APIC.rst
91 	Don't check the IO-APIC timer. This can work around
92 	problems with incorrect timer initialization on some boards.
115     Please note that on systems with MONITOR/MWAIT support (like Intel EM64T
116     CPUs) this option has no performance advantage over the normal idle loop.
124         Use the CPU reboot vector for warm reset
130         Force a triple fault (init)
132         Use the keyboard controller. cold reset (default)
135         the ACPI reset does not work, the reboot path attempts the reset
139         the EFI reset does not work, the reboot path attempts the reset using
144    Using warm reset will be much faster especially on big memory
147    on reboot so there may be boot problems on some systems.
150      Don't stop other CPUs on reboot. This can make reboot more reliable
154      There are some built-in platform specific "quirks" - you may see:
157      newer BIOS, or newer board) using this option will ignore the built-in
170     Don't parse the HMAT table for NUMA setup, or soft-reserved memory
181     Force ACPI on (currently not needed)
205   pci=assign-busses
210     Scan up to NUMBER busses, no matter what the mptable says.
216 Multiple x86-64 PCI-DMA mapping implementations exist, for example:
218    1. <kernel/dma/direct.c>: use no hardware/software IOMMU at all
220       Kernel boot message: "PCI-DMA: Disabling IOMMU"
223       Kernel boot message: "PCI-DMA: using GART IOMMU"
225    3. <arch/x86_64/kernel/pci-swiotlb.c> : Software IOMMU implementation. Used
226       e.g. if there is no hardware IOMMU in the system and it is need because
228       Kernel boot message: "PCI-DMA: Using software bounce buffering
258       Flush IOMMU on each allocation (default).
265       Do scatter-gather (SG) merging. Implies "force" (experimental).
267       Don't do scatter-gather (SG) merging.