linux-kernel - Re: [PATCH v2] KVM: VMX: add MSR_IA32_TSX_CTRL into msrs_to

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Date:   Mon, 8 May 2023 09:54:04 +0800
From:   Xiaoyao Li <xiaoyao.li@...el.com>
To:     Mingwei Zhang <mizhang@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     "H. Peter Anvin" <hpa@...or.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Jim Mattson <jmattson@...gle.com>
Subject: Re: [PATCH v2] KVM: VMX: add MSR_IA32_TSX_CTRL into msrs_to_save

On 5/5/2023 2:18 AM, Mingwei Zhang wrote:
> Add MSR_IA32_TSX_CTRL into msrs_to_save[] to explicitly tell userspace to
> save/restore the register value during migration. Missing this may cause
> userspace that relies on KVM ioctl(KVM_GET_MSR_INDEX_LIST) fail to port the
> value to the target VM.
> 
> In addition, there is no need to add MSR_IA32_TSX_CTRL when
> ARCH_CAP_TSX_CTRL_MSR is not supported in guest. So add the checking in
> kvm_probe_msr_to_save().
> 
> Fixes: b07a5c53d42a ("KVM: vmx: use MSR_IA32_TSX_CTRL to hard-disable TSX on guest that lack it")

I wonder it's the fix for this commit.

Apart from this,

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

> Reported-by: Jim Mattson <jmattson@...gle.com>
> Signed-off-by: Mingwei Zhang <mizhang@...gle.com>
> ---
>   arch/x86/kvm/x86.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 237c483b1230..c8accbd6c861 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1431,7 +1431,7 @@ static const u32 msrs_to_save_base[] = {
>   #endif
>   	MSR_IA32_TSC, MSR_IA32_CR_PAT, MSR_VM_HSAVE_PA,
>   	MSR_IA32_FEAT_CTL, MSR_IA32_BNDCFGS, MSR_TSC_AUX,
> -	MSR_IA32_SPEC_CTRL,
> +	MSR_IA32_SPEC_CTRL, MSR_IA32_TSX_CTRL,
>   	MSR_IA32_RTIT_CTL, MSR_IA32_RTIT_STATUS, MSR_IA32_RTIT_CR3_MATCH,
>   	MSR_IA32_RTIT_OUTPUT_BASE, MSR_IA32_RTIT_OUTPUT_MASK,
>   	MSR_IA32_RTIT_ADDR0_A, MSR_IA32_RTIT_ADDR0_B,
> @@ -7077,6 +7077,10 @@ static void kvm_probe_msr_to_save(u32 msr_index)
>   		if (!kvm_cpu_cap_has(X86_FEATURE_XFD))
>   			return;
>   		break;
> +	case MSR_IA32_TSX_CTRL:
> +		if (!(kvm_get_arch_capabilities() & ARCH_CAP_TSX_CTRL_MSR))
> +			return;
> +		break;
>   	default:
>   		break;
>   	}