Commit f41dd67d authored by Yan-Jie Wang's avatar Yan-Jie Wang Committed by Jonathan Corbet
Browse files

docs: clarify KVM related kernel parameters' descriptions 



The descriptions of certain KVM related kernel parameters can be
confusing. They state "Disable ...," which may make people think that
setting them to 1 will disable the associated feature when in fact the
opposite is true.

This commit addresses this issue by revising the descriptions of these
parameters by using "Control..." rather than "Enable/Disable...".
1==enabled or 0==disabled can be communicated by the description of
default value such as "1 (enabled)" or "0 (disabled)".

Also update the description of KVM's default value for kvm-intel.nested
as it is enabled by default.

Signed-off-by: default avatarYan-Jie Wang <yanjiewtw@gmail.com>
Signed-off-by: default avatarJonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20230503081530.19956-1-yanjiewtw@gmail.com
parent 3c591cc9

Documentation/admin-guide/kernel-parameters.txt

+29 −24
Original line number Diff line number Diff line
@@ -2561,12 +2561,13 @@ 
			If the value is 0 (the default), KVM will pick a period based

			on the ratio, such that a page is zapped after 1 hour on average.



	kvm-amd.nested=	[KVM,AMD] Allow nested virtualization in KVM/SVM.

			Default is 1 (enabled)

	kvm-amd.nested=	[KVM,AMD] Control nested virtualization feature in

			KVM/SVM. Default is 1 (enabled).



	kvm-amd.npt=	[KVM,AMD] Disable nested paging (virtualized MMU)

			for all guests.

			Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.

	kvm-amd.npt=	[KVM,AMD] Control KVM's use of Nested Page Tables,

			a.k.a. Two-Dimensional Page Tables. Default is 1

			(enabled). Disable by KVM if hardware lacks support

			for NPT.



	kvm-arm.mode=

			[KVM,ARM] Select one of KVM/arm64's modes of operation.
@@ -2612,30 +2613,33 @@ 
			Format: <integer>

			Default: 5



	kvm-intel.ept=	[KVM,Intel] Disable extended page tables

			(virtualized MMU) support on capable Intel chips.

			Default is 1 (enabled)

	kvm-intel.ept=	[KVM,Intel] Control KVM's use of Extended Page Tables,

			a.k.a. Two-Dimensional Page Tables.  Default is 1

			(enabled). Disable by KVM if hardware lacks support

			for EPT.



	kvm-intel.emulate_invalid_guest_state=

			[KVM,Intel] Disable emulation of invalid guest state.

			Ignored if kvm-intel.enable_unrestricted_guest=1, as

			guest state is never invalid for unrestricted guests.

			This param doesn't apply to nested guests (L2), as KVM

			never emulates invalid L2 guest state.

			Default is 1 (enabled)

			[KVM,Intel] Control whether to emulate invalid guest

			state. Ignored if kvm-intel.enable_unrestricted_guest=1,

			as guest state is never invalid for unrestricted

			guests. This param doesn't apply to nested guests (L2),

			as KVM never emulates invalid L2 guest state.

			Default is 1 (enabled).



	kvm-intel.flexpriority=

			[KVM,Intel] Disable FlexPriority feature (TPR shadow).

			Default is 1 (enabled)

			[KVM,Intel] Control KVM's use of FlexPriority feature

			(TPR shadow). Default is 1 (enabled). Disalbe by KVM if

			hardware lacks support for it.



	kvm-intel.nested=

			[KVM,Intel] Enable VMX nesting (nVMX).

			Default is 0 (disabled)

			[KVM,Intel] Control nested virtualization feature in

			KVM/VMX. Default is 1 (enabled).



	kvm-intel.unrestricted_guest=

			[KVM,Intel] Disable unrestricted guest feature

			(virtualized real and unpaged mode) on capable

			Intel chips. Default is 1 (enabled)

			[KVM,Intel] Control KVM's use of unrestricted guest

			feature (virtualized real and unpaged mode). Default

			is 1 (enabled). Disable by KVM if EPT is disabled or

			hardware lacks support for it.



	kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault

			CVE-2018-3620.
@@ -2649,9 +2653,10 @@ 


			Default is cond (do L1 cache flush in specific instances)



	kvm-intel.vpid=	[KVM,Intel] Disable Virtual Processor Identification

			feature (tagged TLBs) on capable Intel chips.

			Default is 1 (enabled)

	kvm-intel.vpid=	[KVM,Intel] Control KVM's use of Virtual Processor

			Identification feature (tagged TLBs). Default is 1

			(enabled). Disable by KVM if hardware lacks support

			for it.



	l1d_flush=	[X86,INTEL]

			Control mitigation for L1D based snooping vulnerability.