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SubjectRe: [PATCH v8 4/4] kvm: vmx: Raise #UD on unsupported XSAVES/XRSTORS
Reviewed-by: Jim Mattson <jmattson@google.com>

On Thu, Aug 24, 2017 at 9:09 AM, Paolo Bonzini <pbonzini@redhat.com> wrote:
> A guest may not be configured to support XSAVES/XRSTORS, even when the host
> does. If the guest does not support XSAVES/XRSTORS, clear the secondary
> execution control so that the processor will raise #UD.
>
> Also clear the "allowed-1" bit for XSAVES/XRSTORS exiting in the
> IA32_VMX_PROCBASED_CTLS2 MSR, and pass through VMCS12's control in
> the VMCS02.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
> arch/x86/kvm/vmx.c | 26 ++++++++++++++++++++++----
> 1 file changed, 22 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 954e26079cd6..08bfeb8c32ea 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -1358,8 +1358,7 @@ static inline int nested_cpu_has_ept(struct vmcs12 *vmcs12)
>
> static inline bool nested_cpu_has_xsaves(struct vmcs12 *vmcs12)
> {
> - return nested_cpu_has2(vmcs12, SECONDARY_EXEC_XSAVES) &&
> - vmx_xsaves_supported();
> + return nested_cpu_has2(vmcs12, SECONDARY_EXEC_XSAVES);
> }
>
> static inline bool nested_cpu_has_pml(struct vmcs12 *vmcs12)
> @@ -2823,8 +2822,7 @@ static void nested_vmx_setup_ctls_msrs(struct vcpu_vmx *vmx)
> SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE |
> SECONDARY_EXEC_APIC_REGISTER_VIRT |
> SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY |
> - SECONDARY_EXEC_WBINVD_EXITING |
> - SECONDARY_EXEC_XSAVES;
> + SECONDARY_EXEC_WBINVD_EXITING;
>
> if (enable_ept) {
> /* nested EPT: emulate EPT also to L1 */
> @@ -5319,6 +5317,25 @@ static void vmx_compute_secondary_exec_control(struct vcpu_vmx *vmx)
> if (!enable_pml)
> exec_control &= ~SECONDARY_EXEC_ENABLE_PML;
>
> + if (vmx_xsaves_supported()) {
> + /* Exposing XSAVES only when XSAVE is exposed */
> + bool xsaves_enabled =
> + guest_cpuid_has(vcpu, X86_FEATURE_XSAVE) &&
> + guest_cpuid_has(vcpu, X86_FEATURE_XSAVES);
> +
> + if (!xsaves_enabled)
> + exec_control &= ~SECONDARY_EXEC_XSAVES;
> +
> + if (nested) {
> + if (xsaves_enabled)
> + vmx->nested.nested_vmx_secondary_ctls_high |=
> + SECONDARY_EXEC_XSAVES;
> + else
> + vmx->nested.nested_vmx_secondary_ctls_high &=
> + ~SECONDARY_EXEC_XSAVES;
> + }
> + }
> +
> if (vmx_rdtscp_supported()) {
> bool rdtscp_enabled = guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP);
> if (!rdtscp_enabled)
> @@ -10421,6 +10438,7 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
> exec_control &= ~(SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES |
> SECONDARY_EXEC_ENABLE_INVPCID |
> SECONDARY_EXEC_RDTSCP |
> + SECONDARY_EXEC_XSAVES |
> SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY |
> SECONDARY_EXEC_APIC_REGISTER_VIRT |
> SECONDARY_EXEC_ENABLE_VMFUNC);
> --
> 1.8.3.1
>

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