On 20/05/2015 22:41, Liang Li wrote:
> The MPX feature requires eager KVM FPU restore support. We have verified
> that MPX cannot work correctly with the current lazy KVM FPU restore
> mechanism. Eager KVM FPU restore should be enabled if the MPX feature is
> exposed to VM.
>
> Signed-off-by: Liang Li <liang.z.li@xxxxxxxxx>
> Signed-off-by: Yang Zhang <yang.z.zhang@xxxxxxxxx>
> ---
> arch/x86/include/asm/kvm_host.h | 1 +
> arch/x86/kvm/cpuid.c | 4 ++++
> arch/x86/kvm/cpuid.h | 8 ++++++++
> arch/x86/kvm/vmx.c | 5 +++++
> arch/x86/kvm/x86.c | 3 ++-
> 5 files changed, 20 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index e61c3a4..4cb39d4 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -401,6 +401,7 @@ struct kvm_vcpu_arch {
> struct kvm_mmu_memory_cache mmu_page_header_cache;
>
> struct fpu guest_fpu;
> + bool eager_fpu;
> u64 xcr0;
> u64 guest_supported_xcr0;
> u32 guest_xstate_size;
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 59b69f6..5ac5e4d 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -95,6 +95,10 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu)
> if (best && (best->eax & (F(XSAVES) | F(XSAVEC))))
> best->ebx = xstate_required_size(vcpu->arch.xcr0, true);
>
> + if (guest_cpuid_has_mpx(vcpu))
> + vcpu->arch.eager_fpu = true;
> + else
> + vcpu->arch.eager_fpu = false;
> /*
> * The existing code assumes virtual address is 48-bit in the canonical
> * address checks; exit if it is ever changed.
> diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
> index c3b1ad9..496b369 100644
> --- a/arch/x86/kvm/cpuid.h
> +++ b/arch/x86/kvm/cpuid.h
> @@ -117,4 +117,12 @@ static inline bool guest_cpuid_has_rtm(struct kvm_vcpu *vcpu)
> best = kvm_find_cpuid_entry(vcpu, 7, 0);
> return best && (best->ebx & bit(X86_FEATURE_RTM));
> }
> +
> +static inline bool guest_cpuid_has_mpx(struct kvm_vcpu *vcpu)
> +{
> + struct kvm_cpuid_entry2 *best;
> +
> + best = kvm_find_cpuid_entry(vcpu, 7, 0);
> + return best && (best->ebx & bit(X86_FEATURE_MPX));
> +}
> #endif
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index f7b6168..7082151 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -8445,6 +8445,11 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
> goto free_vmcs;
> }
>
> + /*
> + * activate fpu here is okay, because it will be deactivated soon if the
> + * lazy fpu restore mode is used.
> + */
> + vmx_fpu_activate(&vmx->vcpu);
> return &vmx->vcpu;
>
> free_vmcs:
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 5f38188..4d9f8e9 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7060,7 +7060,8 @@ void kvm_put_guest_fpu(struct kvm_vcpu *vcpu)
> fpu_save_init(&vcpu->arch.guest_fpu);
> __kernel_fpu_end();
> ++vcpu->stat.fpu_reload;
> - kvm_make_request(KVM_REQ_DEACTIVATE_FPU, vcpu);
> + if (!vcpu->arch.eager_fpu)
> + kvm_make_request(KVM_REQ_DEACTIVATE_FPU, vcpu);
> trace_kvm_fpu(0);
> }
>
>
Thanks, applied to kvm/master.
Paolo
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