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SubjectRe: [PATCH] KVM: x86: Fix xsave cpuid exposing bug
Il 21/02/2014 18:39, Liu, Jinsong ha scritto:
> From 00c920c96127d20d4c3bb790082700ae375c39a0 Mon Sep 17 00:00:00 2001
> From: Liu Jinsong <jinsong.liu@intel.com>
> Date: Fri, 21 Feb 2014 23:47:18 +0800
> Subject: [PATCH] KVM: x86: Fix xsave cpuid exposing bug
>
> EBX of cpuid(0xD, 0) is dynamic per XCR0 features enable/disable.
> Bit 63 of XCR0 is reserved for future expansion.
>
> Signed-off-by: Liu Jinsong <jinsong.liu@intel.com>
> ---
> arch/x86/include/asm/xsave.h | 2 ++
> arch/x86/kvm/cpuid.c | 6 +++---
> arch/x86/kvm/x86.c | 7 +++++--
> 3 files changed, 10 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/include/asm/xsave.h b/arch/x86/include/asm/xsave.h
> index 5547389..dcd047b 100644
> --- a/arch/x86/include/asm/xsave.h
> +++ b/arch/x86/include/asm/xsave.h
> @@ -13,6 +13,8 @@
> #define XSTATE_BNDCSR 0x10
>
> #define XSTATE_FPSSE (XSTATE_FP | XSTATE_SSE)
> +/* Bit 63 of XCR0 is reserved for future expansion */
> +#define XSTATE_EXTEND_MASK (~(XSTATE_FPSSE | (1ULL << 63)))
>
> #define FXSAVE_SIZE 512
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index a951ae4..b241325 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -28,7 +28,7 @@ static u32 xstate_required_size(u64 xstate_bv)
> int feature_bit = 0;
> u32 ret = XSAVE_HDR_SIZE + XSAVE_HDR_OFFSET;
>
> - xstate_bv &= ~XSTATE_FPSSE;
> + xstate_bv &= XSTATE_EXTEND_MASK;
> while (xstate_bv) {
> if (xstate_bv & 0x1) {
> u32 eax, ebx, ecx, edx;
> @@ -74,8 +74,8 @@ void kvm_update_cpuid(struct kvm_vcpu *vcpu)
> vcpu->arch.guest_supported_xcr0 =
> (best->eax | ((u64)best->edx << 32)) &
> host_xcr0 & KVM_SUPPORTED_XCR0;
> - vcpu->arch.guest_xstate_size =
> - xstate_required_size(vcpu->arch.guest_supported_xcr0);
> + vcpu->arch.guest_xstate_size = best->ebx =
> + xstate_required_size(vcpu->arch.xcr0);
> }
>
> kvm_pmu_cpuid_update(vcpu);
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 39c28f0..7c52acb 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -595,13 +595,13 @@ static void kvm_put_guest_xcr0(struct kvm_vcpu *vcpu)
>
> int __kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr)
> {
> - u64 xcr0;
> + u64 xcr0 = xcr;
> + u64 old_xcr0 = vcpu->arch.xcr0;
> u64 valid_bits;
>
> /* Only support XCR_XFEATURE_ENABLED_MASK(xcr0) now */
> if (index != XCR_XFEATURE_ENABLED_MASK)
> return 1;
> - xcr0 = xcr;
> if (!(xcr0 & XSTATE_FP))
> return 1;
> if ((xcr0 & XSTATE_YMM) && !(xcr0 & XSTATE_SSE))
> @@ -618,6 +618,9 @@ int __kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr)
>
> kvm_put_guest_xcr0(vcpu);
> vcpu->arch.xcr0 = xcr0;
> +
> + if ((xcr0 ^ old_xcr0) & XSTATE_EXTEND_MASK)
> + kvm_update_cpuid(vcpu);
> return 0;
> }
>
>

Applied to kvm/queue, thanks.

Paolo



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