linux-kernel - Re: [PATCH 4/6] KVM: x86: Move MSR_IA32_PRED

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Date:   Mon, 27 Mar 2023 14:41:48 +0800
From:   Xiaoyao Li <xiaoyao.li@...el.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Nathan Chancellor <nathan@...nel.org>,
        Emanuele Giuseppe Esposito <eesposit@...hat.com>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Jim Mattson <jmattson@...gle.com>
Subject: Re: [PATCH 4/6] KVM: x86: Move MSR_IA32_PRED_CMD WRMSR emulation to
 common code

On 3/22/2023 9:14 AM, Sean Christopherson wrote:
> Dedup the handling of MSR_IA32_PRED_CMD across VMX and SVM by moving the
> logic to kvm_set_msr_common().  Now that the MSR interception toggling is
> handled as part of setting guest CPUID, the VMX and SVM paths are
> identical.
> 
> Opportunistically massage the code to make it a wee bit denser.
> 

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

> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>   arch/x86/kvm/svm/svm.c | 14 --------------
>   arch/x86/kvm/vmx/vmx.c | 14 --------------
>   arch/x86/kvm/x86.c     | 11 +++++++++++
>   3 files changed, 11 insertions(+), 28 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index f757b436ffae..85bb535fc321 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -2942,20 +2942,6 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
>   		 */
>   		set_msr_interception(vcpu, svm->msrpm, MSR_IA32_SPEC_CTRL, 1, 1);
>   		break;
> -	case MSR_IA32_PRED_CMD:
> -		if (!msr->host_initiated &&
> -		    !guest_has_pred_cmd_msr(vcpu))
> -			return 1;
> -
> -		if (data & ~PRED_CMD_IBPB)
> -			return 1;
> -		if (!boot_cpu_has(X86_FEATURE_IBPB))
> -			return 1;
> -		if (!data)
> -			break;
> -
> -		wrmsrl(MSR_IA32_PRED_CMD, PRED_CMD_IBPB);
> -		break;
>   	case MSR_AMD64_VIRT_SPEC_CTRL:
>   		if (!msr->host_initiated &&
>   		    !guest_cpuid_has(vcpu, X86_FEATURE_VIRT_SSBD))
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 5c01c76c0d45..29807be219b9 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -2285,20 +2285,6 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>   		if (data & ~(TSX_CTRL_RTM_DISABLE | TSX_CTRL_CPUID_CLEAR))
>   			return 1;
>   		goto find_uret_msr;
> -	case MSR_IA32_PRED_CMD:
> -		if (!msr_info->host_initiated &&
> -		    !guest_has_pred_cmd_msr(vcpu))
> -			return 1;
> -
> -		if (data & ~PRED_CMD_IBPB)
> -			return 1;
> -		if (!boot_cpu_has(X86_FEATURE_IBPB))
> -			return 1;
> -		if (!data)
> -			break;
> -
> -		wrmsrl(MSR_IA32_PRED_CMD, PRED_CMD_IBPB);
> -		break;
>   	case MSR_IA32_CR_PAT:
>   		if (!kvm_pat_valid(data))
>   			return 1;
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 237c483b1230..c83ec88da043 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3617,6 +3617,17 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>   		vcpu->arch.perf_capabilities = data;
>   		kvm_pmu_refresh(vcpu);
>   		return 0;
> +	case MSR_IA32_PRED_CMD:
> +		if (!msr_info->host_initiated && !guest_has_pred_cmd_msr(vcpu))
> +			return 1;
> +
> +		if (!boot_cpu_has(X86_FEATURE_IBPB) || (data & ~PRED_CMD_IBPB))
> +			return 1;
> +		if (!data)
> +			break;
> +
> +		wrmsrl(MSR_IA32_PRED_CMD, PRED_CMD_IBPB);
> +		break;
>   	case MSR_EFER:
>   		return set_efer(vcpu, msr_info);
>   	case MSR_K7_HWCR: