From mboxrd@z Thu Jan 1 00:00:00 1970 From: Glauber Costa Subject: [PATCH 9/9] Add cpuid.txt file Date: Tue, 11 May 2010 12:17:47 -0400 Message-ID: <1273594667-17175-10-git-send-email-glommer@redhat.com> References: <1273594667-17175-1-git-send-email-glommer@redhat.com> <1273594667-17175-2-git-send-email-glommer@redhat.com> <1273594667-17175-3-git-send-email-glommer@redhat.com> <1273594667-17175-4-git-send-email-glommer@redhat.com> <1273594667-17175-5-git-send-email-glommer@redhat.com> <1273594667-17175-6-git-send-email-glommer@redhat.com> <1273594667-17175-7-git-send-email-glommer@redhat.com> <1273594667-17175-8-git-send-email-glommer@redhat.com> <1273594667-17175-9-git-send-email-glommer@redhat.com> Cc: linux-kernel@vger.kernel.org, avi@redhat.com, zamsden@redhat.com To: kvm@vger.kernel.org Return-path: In-Reply-To: <1273594667-17175-9-git-send-email-glommer@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org This file documents cpuid bits used by KVM. Signed-off-by: Glauber Costa --- Documentation/kvm/cpuid.txt | 44 +++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 44 insertions(+), 0 deletions(-) create mode 100644 Documentation/kvm/cpuid.txt diff --git a/Documentation/kvm/cpuid.txt b/Documentation/kvm/cpuid.txt new file mode 100644 index 0000000..ca1e89f --- /dev/null +++ b/Documentation/kvm/cpuid.txt @@ -0,0 +1,44 @@ +KVM CPUID bits +Glauber Costa , Red Hat Inc, 2010 +===================================================== + +A guest running on a kvm host, can check some of its features using +cpuid. This is not always guaranteed to work, since userspace can +mask-out some, or even all KVM-related cpuid features before launching +a guest. + +KVM cpuid functions are: + +function: KVM_CPUID_SIGNATURE (0x40000000) +returns : eax = 0, + ebx = 0x4b4d564b, + ecx = 0x564b4d56, + edx = 0x4d. +Note that this value in ebx, ecx and edx corresponds to the string "KVMKVMKVM". +This function queries the presence of KVM cpuid leafs. + + +function: define KVM_CPUID_FEATURES (0x40000001) +returns : ebx, ecx, edx = 0 + eax = and OR'ed group of (1 << flag), where each flags is: + + +flag || value || meaning +============================================================================= +KVM_FEATURE_CLOCKSOURCE || 0 || kvmclock available at msrs + || || 0x11 and 0x12. +------------------------------------------------------------------------------ +KVM_FEATURE_NOP_IO_DELAY || 1 || not necessary to perform delays + || || on PIO operations. +------------------------------------------------------------------------------ +KVM_FEATURE_MMU_OP || 2 || deprecated. +------------------------------------------------------------------------------ +KVM_FEATURE_CLOCKSOURCE2 || 3 || kvmclock available at msrs + || || 0x4b564d00 and 0x4b564d01 +------------------------------------------------------------------------------ +KVM_FEATURE_CLOCKSOURCE_STABLE_BIT || 24 || host will wanr if no guest-side + || || per-cpu warps are expected in + || || kvmclock. +------------------------------------------------------------------------------ + + -- 1.6.2.2