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[2/6] KVM: VMX: Passthrough MSR_IA32_PRED_CMD based purely on host+guest CPUID

Message ID 20230322011440.2195485-3-seanjc@google.com
State New
Headers
Series KVM: x86: Unhost the *_CMD MSR mess |

Commit Message

Sean Christopherson March 22, 2023, 1:14 a.m. UTC 
  Passthrough MSR_IA32_PRED_CMD based purely on whether or not the MSR is
supported and enabled, i.e. don't wait until the first write.  There's no
benefit to deferred passthrough, and the extra logic only adds complexity.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/vmx/vmx.c | 16 +++-------------
 1 file changed, 3 insertions(+), 13 deletions(-)

Comments

Xiaoyao Li March 27, 2023, 3:46 a.m. UTC | #1 
On 3/22/2023 9:14 AM, Sean Christopherson wrote:
> Passthrough MSR_IA32_PRED_CMD based purely on whether or not the MSR is
> supported and enabled, i.e. don't wait until the first write.  There's no
> benefit to deferred passthrough, and the extra logic only adds complexity.

Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>

> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
>   arch/x86/kvm/vmx/vmx.c | 16 +++-------------
>   1 file changed, 3 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index f777509ecf17..5c01c76c0d45 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -2298,19 +2298,6 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>   			break;
>   
>   		wrmsrl(MSR_IA32_PRED_CMD, PRED_CMD_IBPB);
> -
> -		/*
> -		 * For non-nested:
> -		 * When it's written (to non-zero) for the first time, pass
> -		 * it through.
> -		 *
> -		 * For nested:
> -		 * The handling of the MSR bitmap for L2 guests is done in
> -		 * nested_vmx_prepare_msr_bitmap. We should not touch the
> -		 * vmcs02.msr_bitmap here since it gets completely overwritten
> -		 * in the merging.
> -		 */
> -		vmx_disable_intercept_for_msr(vcpu, MSR_IA32_PRED_CMD, MSR_TYPE_W);
>   		break;
>   	case MSR_IA32_CR_PAT:
>   		if (!kvm_pat_valid(data))
> @@ -7743,6 +7730,9 @@ static void vmx_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
>   		vmx_set_intercept_for_msr(vcpu, MSR_IA32_XFD_ERR, MSR_TYPE_R,
>   					  !guest_cpuid_has(vcpu, X86_FEATURE_XFD));
>   
> +	if (boot_cpu_has(X86_FEATURE_IBPB))
> +		vmx_set_intercept_for_msr(vcpu, MSR_IA32_PRED_CMD, MSR_TYPE_W,
> +					  !guest_has_pred_cmd_msr(vcpu));
>   
>   	set_cr4_guest_host_mask(vmx);
>
diff mbox series

Patch

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index f777509ecf17..5c01c76c0d45 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2298,19 +2298,6 @@  static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 			break;
 
 		wrmsrl(MSR_IA32_PRED_CMD, PRED_CMD_IBPB);
-
-		/*
-		 * For non-nested:
-		 * When it's written (to non-zero) for the first time, pass
-		 * it through.
-		 *
-		 * For nested:
-		 * The handling of the MSR bitmap for L2 guests is done in
-		 * nested_vmx_prepare_msr_bitmap. We should not touch the
-		 * vmcs02.msr_bitmap here since it gets completely overwritten
-		 * in the merging.
-		 */
-		vmx_disable_intercept_for_msr(vcpu, MSR_IA32_PRED_CMD, MSR_TYPE_W);
 		break;
 	case MSR_IA32_CR_PAT:
 		if (!kvm_pat_valid(data))
@@ -7743,6 +7730,9 @@  static void vmx_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
 		vmx_set_intercept_for_msr(vcpu, MSR_IA32_XFD_ERR, MSR_TYPE_R,
 					  !guest_cpuid_has(vcpu, X86_FEATURE_XFD));
 
+	if (boot_cpu_has(X86_FEATURE_IBPB))
+		vmx_set_intercept_for_msr(vcpu, MSR_IA32_PRED_CMD, MSR_TYPE_W,
+					  !guest_has_pred_cmd_msr(vcpu));
 
 	set_cr4_guest_host_mask(vmx);