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Date: Wed, 2 May 2012 17:55:56 +0300 From: "Michael S. Tsirkin" <mst@...hat.com> To: kvm@...r.kernel.org Cc: Rob Landley <rob@...dley.net>, Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org, gleb@...hat.com, Randy Dunlap <randy.dunlap@...cle.com>, linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org Subject: [PATCHv2] kvm: fix cpuid eax cpuid eax should return the max leaf so that guests can find out the valid range. This matches Xen et al. Update documentation to match. Tested with -cpu host. Signed-off-by: Michael S. Tsirkin <mst@...hat.com> --- Changes from v1: Updated documentation. Documentation/virtual/kvm/cpuid.txt | 6 +++++- arch/x86/kvm/cpuid.c | 2 +- 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/Documentation/virtual/kvm/cpuid.txt b/Documentation/virtual/kvm/cpuid.txt index 8820685..83afe65 100644 --- a/Documentation/virtual/kvm/cpuid.txt +++ b/Documentation/virtual/kvm/cpuid.txt @@ -10,11 +10,15 @@ a guest. KVM cpuid functions are: function: KVM_CPUID_SIGNATURE (0x40000000) -returns : eax = 0, +returns : eax = 0x40000001, ebx = 0x4b4d564b, ecx = 0x564b4d56, edx = 0x4d. Note that this value in ebx, ecx and edx corresponds to the string "KVMKVMKVM". +The value in eax corresponds to the maximum cpuid function present in this leaf, +and will be updated if more functions are added in the future. +Note also that old hosts set eax value to 0x0. This should +be interpreted as if the value was 0x40000001. This function queries the presence of KVM cpuid leafs. diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 9fed5be..eba8345 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -397,7 +397,7 @@ static int do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, case KVM_CPUID_SIGNATURE: { char signature[12] = "KVMKVMKVM\0\0"; u32 *sigptr = (u32 *)signature; - entry->eax = 0; + entry->eax = KVM_CPUID_FEATURES; entry->ebx = sigptr[0]; entry->ecx = sigptr[1]; entry->edx = sigptr[2]; -- MST -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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