Re: [PATCH v7 13/15] KVM: x86/vmx: Clear Arch LBREn bit before inject #DB to guest

[Like Xu]

On 6/8/2021 3:42 pm, Yang Weijiang wrote:
> Per ISA spec, need to clear the bit before inject #DB.

Please paste the SDM statement accurately so that the reviewers
can verify that the code is consistent with the documentation.

> Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
> ---
>   arch/x86/kvm/vmx/vmx.c | 21 +++++++++++++++++++++
>   1 file changed, 21 insertions(+)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 70314cd93340..31b9c06c9b3b 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -1601,6 +1601,21 @@ static void vmx_clear_hlt(struct kvm_vcpu *vcpu)
>   		vmcs_write32(GUEST_ACTIVITY_STATE, GUEST_ACTIVITY_ACTIVE);
>   }
>   
> +static void flip_arch_lbr_ctl(struct kvm_vcpu *vcpu, bool on)
> +{
> +	if (vcpu_to_pmu(vcpu)->event_count > 0 &&

Ugh, this check seems ridiculous/funny to me.

> +	    kvm_cpu_cap_has(X86_FEATURE_ARCH_LBR)) {
> +		u64 lbr_ctl = vmcs_read64(GUEST_IA32_LBR_CTL);
> +
> +		if (on)
> +			lbr_ctl |= 1ULL;
> +		else
> +			lbr_ctl &= ~1ULL;
> +
> +		vmcs_write64(GUEST_IA32_LBR_CTL, lbr_ctl);
> +	}
> +}

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