linux-kernel - Re: [PATCH 1/2] kvm/x86: Move MSR_K7

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Date:   Mon, 25 Mar 2019 11:21:33 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     KVM <kvm@...r.kernel.org>, Joerg Roedel <joro@...tes.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Tony Luck <tony.luck@...el.com>,
        Yazen Ghannam <Yazen.Ghannam@....com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] kvm/x86: Move MSR_K7_HWCR to svm.c

On Mon, Mar 25, 2019 at 06:16:48PM +0100, Borislav Petkov wrote:
> From: Borislav Petkov <bp@...e.de>
> 
> This is an AMD-specific MSR. Put it where it belongs.
> 
> Signed-off-by: Borislav Petkov <bp@...e.de>
> Tested-by: Yazen Ghannam <yazen.ghannam@....com>
> ---
>  arch/x86/kvm/svm.c | 14 ++++++++++++++
>  arch/x86/kvm/x86.c | 12 ------------
>  2 files changed, 14 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index b5b128a0a051..00eb44a2a377 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -4201,6 +4201,9 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  	case MSR_F10H_DECFG:
>  		msr_info->data = svm->msr_decfg;
>  		break;
> +	case MSR_K7_HWCR:
> +		msr_info->data = 0;
> +		break;
>  	default:
>  		return kvm_get_msr_common(vcpu, msr_info);
>  	}
> @@ -4405,6 +4408,17 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
>  		svm->msr_decfg = data;
>  		break;
>  	}
> +	case MSR_K7_HWCR:
> +		data &= ~(u64)0x40;	/* ignore flush filter disable */
> +		data &= ~(u64)0x100;	/* ignore ignne emulation enable */
> +		data &= ~(u64)0x8;	/* ignore TLB cache disable */
> +		data &= ~(u64)0x40000;  /* ignore Mc status write enable */
> +		if (data != 0) {
> +			vcpu_unimpl(vcpu, "unimplemented HWCR wrmsr: 0x%llx\n",
> +				    data);
> +			return 1;
> +		}
> +		break;
>  	case MSR_IA32_APICBASE:
>  		if (kvm_vcpu_apicv_active(vcpu))
>  			avic_update_vapic_bar(to_svm(vcpu), data);
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 65e4559eef2f..e53d13cfceba 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2445,17 +2445,6 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  		break;
>  	case MSR_EFER:
>  		return set_efer(vcpu, data);
> -	case MSR_K7_HWCR:
> -		data &= ~(u64)0x40;	/* ignore flush filter disable */
> -		data &= ~(u64)0x100;	/* ignore ignne emulation enable */
> -		data &= ~(u64)0x8;	/* ignore TLB cache disable */
> -		data &= ~(u64)0x40000;  /* ignore Mc status write enable */
> -		if (data != 0) {
> -			vcpu_unimpl(vcpu, "unimplemented HWCR wrmsr: 0x%llx\n",
> -				    data);
> -			return 1;
> -		}
> -		break;
>  	case MSR_FAM10H_MMIO_CONF_BASE:
>  		if (data != 0) {
>  			vcpu_unimpl(vcpu, "unimplemented MMIO_CONF_BASE wrmsr: "
> @@ -2724,7 +2713,6 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  	case MSR_K8_SYSCFG:
>  	case MSR_K8_TSEG_ADDR:
>  	case MSR_K8_TSEG_MASK:
> -	case MSR_K7_HWCR:

Won't this prevent emulating an AMD guest on Intel hardware, e.g. due to
injecting #GPs during boot?  Keeping support in kvm_{get,set}_msr_common
doesn't preclude svm_{get,set}_msr() from having SVM-specific handling for
the MSR.

>  	case MSR_VM_HSAVE_PA:
>  	case MSR_K8_INT_PENDING_MSG:
>  	case MSR_AMD64_NB_CFG:
> -- 
> 2.21.0
>