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[111.248.114.205]) by smtp.gmail.com with ESMTPSA id jx12-20020a17090b46cc00b0024e0141353dsm782148pjb.28.2023.05.03.01.16.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 May 2023 01:16:39 -0700 (PDT) From: Yan-Jie Wang To: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Jonathan Corbet , Sean Christopherson , Paolo Bonzini , Randy Dunlap , Andre Przywara , Avi Kivity , Yan-Jie Wang , Ching-Chun Huang , trivial@kernel.org, kvm@vger.kernel.org Subject: [PATCH v2] docs: clarify KVM related kernel parameters' descriptions Date: Wed, 3 May 2023 16:15:31 +0800 Message-Id: <20230503081530.19956-1-yanjiewtw@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230502112502.14859-1-yanjiewtw@gmail.com> References: <20230502112502.14859-1-yanjiewtw@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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=3D=3Denabled or 0=3D=3Ddisabled 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 --- Changes in v2: - Revise the descriptions based on Sean's suggesstion. - Fix the wrong default value of kvm-intel.nested --- .../admin-guide/kernel-parameters.txt | 53 ++++++++++--------- 1 file changed, 29 insertions(+), 24 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentatio= n/admin-guide/kernel-parameters.txt index 9e5bab29685f..450c9d3af3ed 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2551,12 +2551,13 @@ 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. =20 - kvm-amd.nested=3D [KVM,AMD] Allow nested virtualization in KVM/SVM. - Default is 1 (enabled) + kvm-amd.nested=3D [KVM,AMD] Control nested virtualization feature in + KVM/SVM. Default is 1 (enabled). =20 - kvm-amd.npt=3D [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=3D [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. =20 kvm-arm.mode=3D [KVM,ARM] Select one of KVM/arm64's modes of operation. @@ -2602,30 +2603,33 @@ Format: Default: 5 =20 - kvm-intel.ept=3D [KVM,Intel] Disable extended page tables - (virtualized MMU) support on capable Intel chips. - Default is 1 (enabled) + kvm-intel.ept=3D [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. =20 kvm-intel.emulate_invalid_guest_state=3D - [KVM,Intel] Disable emulation of invalid guest state. - Ignored if kvm-intel.enable_unrestricted_guest=3D1, 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=3D1, + 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). =20 kvm-intel.flexpriority=3D - [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. =20 kvm-intel.nested=3D - [KVM,Intel] Enable VMX nesting (nVMX). - Default is 0 (disabled) + [KVM,Intel] Control nested virtualization feature in + KVM/VMX. Default is 1 (enabled). =20 kvm-intel.unrestricted_guest=3D - [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. =20 kvm-intel.vmentry_l1d_flush=3D[KVM,Intel] Mitigation for L1 Terminal Fault CVE-2018-3620. @@ -2639,9 +2643,10 @@ =20 Default is cond (do L1 cache flush in specific instances) =20 - kvm-intel.vpid=3D [KVM,Intel] Disable Virtual Processor Identification - feature (tagged TLBs) on capable Intel chips. - Default is 1 (enabled) + kvm-intel.vpid=3D [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. =20 l1d_flush=3D [X86,INTEL] Control mitigation for L1D based snooping vulnerability. base-commit: 865fdb08197e657c59e74a35fa32362b12397f58 --=20 2.34.1