linux-kernel - Re: [PATCH] x86, kvm: Add MSR_AMD64_BU

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Date:	Wed, 13 Feb 2013 13:47:47 +0200
From:	Gleb Natapov <gleb@...hat.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	kvm@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	X86 ML <x86@...nel.org>, Borislav Petkov <bp@...e.de>,
	Boris Ostrovsky <boris.ostrovsky@....com>,
	Andre Przywara <andre@...rep.de>,
	Marcelo Tosatti <mtosatti@...hat.com>
Subject: Re: [PATCH] x86, kvm: Add MSR_AMD64_BU_CFG2 to the list of ignored
 MSRs

On Wed, Feb 13, 2013 at 12:42:41PM +0100, Borislav Petkov wrote:
> From: Borislav Petkov <bp@...e.de>
> 
> The "x86, AMD: Enable WC+ memory type on family 10 processors" patch
> currently in -tip added a workaround for AMD F10h CPUs which #GPs my
> guest when booted in kvm. This is because it accesses MSR_AMD64_BU_CFG2
> which is not currently ignored by kvm. Do that because this MSR is only
> baremetal-relevant anyway. While at it, move the ignored MSRs at the
> beginning of kvm_set_msr_common so that we exit then and there.
> 
Is your guest compiled without PV support? With PV Linux traps #GP for
all MSRs and it saves us in more than one places. 

> Signed-off-by: Borislav Petkov <bp@...e.de>
> Cc: Boris Ostrovsky <boris.ostrovsky@....com>
> Cc: Andre Przywara <andre@...rep.de>
> Cc: Marcelo Tosatti <mtosatti@...hat.com>
> Cc: Gleb Natapov <gleb@...hat.com>
> ---
>  arch/x86/kvm/x86.c | 16 +++++++++-------
>  1 file changed, 9 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index c243b81e3c74..37040079cd6b 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1881,6 +1881,14 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  	u64 data = msr_info->data;
>  
>  	switch (msr) {
> +	case MSR_AMD64_NB_CFG:
> +	case MSR_IA32_UCODE_REV:
> +	case MSR_IA32_UCODE_WRITE:
> +	case MSR_VM_HSAVE_PA:
> +	case MSR_AMD64_PATCH_LOADER:
> +	case MSR_AMD64_BU_CFG2:
> +		break;
> +
>  	case MSR_EFER:
>  		return set_efer(vcpu, data);
>  	case MSR_K7_HWCR:
> @@ -1900,8 +1908,6 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  			return 1;
>  		}
>  		break;
> -	case MSR_AMD64_NB_CFG:
> -		break;
>  	case MSR_IA32_DEBUGCTLMSR:
>  		if (!data) {
>  			/* We support the non-activated case already */
> @@ -1914,11 +1920,6 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  		vcpu_unimpl(vcpu, "%s: MSR_IA32_DEBUGCTLMSR 0x%llx, nop\n",
>  			    __func__, data);
>  		break;
> -	case MSR_IA32_UCODE_REV:
> -	case MSR_IA32_UCODE_WRITE:
> -	case MSR_VM_HSAVE_PA:
> -	case MSR_AMD64_PATCH_LOADER:
> -		break;
>  	case 0x200 ... 0x2ff:
>  		return set_msr_mtrr(vcpu, msr, data);
>  	case MSR_IA32_APICBASE:
> @@ -2253,6 +2254,7 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
>  	case MSR_K8_INT_PENDING_MSG:
>  	case MSR_AMD64_NB_CFG:
>  	case MSR_FAM10H_MMIO_CONF_BASE:
> +	case MSR_AMD64_BU_CFG2:
>  		data = 0;
>  		break;
>  	case MSR_P6_PERFCTR0:
> -- 
> 1.8.1.3.535.ga923c31

--
			Gleb.
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