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

			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.

			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.

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

			Default is 1 (enabled)

			KVM/SVM. Default is 1 (enabled).





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

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

			for all guests.

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

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

			(enabled). Disable by KVM if hardware lacks support

			for NPT.





	kvm-arm.mode=

	kvm-arm.mode=

			[KVM,ARM] Select one of KVM/arm64's modes of operation.

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

			Format: <integer>

			Default: 5

			Default: 5





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

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

			(virtualized MMU) support on capable Intel chips.

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

			Default is 1 (enabled)

			(enabled). Disable by KVM if hardware lacks support

			for EPT.





	kvm-intel.emulate_invalid_guest_state=

	kvm-intel.emulate_invalid_guest_state=

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

			[KVM,Intel] Control whether to emulate invalid guest

			Ignored if kvm-intel.enable_unrestricted_guest=1, as

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

			guest state is never invalid for unrestricted guests.

			as guest state is never invalid for unrestricted

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

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

			never emulates invalid L2 guest state.

			as KVM never emulates invalid L2 guest state.

			Default is 1 (enabled)

			Default is 1 (enabled).





	kvm-intel.flexpriority=

	kvm-intel.flexpriority=

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

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

			Default is 1 (enabled)

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

			hardware lacks support for it.





	kvm-intel.nested=

	kvm-intel.nested=

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

			[KVM,Intel] Control nested virtualization feature in

			Default is 0 (disabled)

			KVM/VMX. Default is 1 (enabled).





	kvm-intel.unrestricted_guest=

	kvm-intel.unrestricted_guest=

			[KVM,Intel] Disable unrestricted guest feature

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

			(virtualized real and unpaged mode) on capable

			feature (virtualized real and unpaged mode). Default

			Intel chips. Default is 1 (enabled)

			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

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

			CVE-2018-3620.

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




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

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





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

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

			feature (tagged TLBs) on capable Intel chips.

			Identification feature (tagged TLBs). Default is 1

			Default is 1 (enabled)

			(enabled). Disable by KVM if hardware lacks support

			for it.





	l1d_flush=	[X86,INTEL]

	l1d_flush=	[X86,INTEL]

			Control mitigation for L1D based snooping vulnerability.

			Control mitigation for L1D based snooping vulnerability.