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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: Yan-Jie Wang <yanjiewtw@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20230503081530.19956-1-yanjiewtw@gmail.com
This commit is contained in:
Yan-Jie Wang 2023-05-03 16:15:31 +08:00 committed by Jonathan Corbet
parent 3c591cc954
commit f41dd67da6
1 changed files with 29 additions and 24 deletions
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53
Documentation/admin-guide/kernel-parameters.txt
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@ -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.