Re: [PATCH v3 2/7] KVM: x86: nSVM: implement nested LBR virtualization

[Paolo Bonzini <pbonzini@xxxxxxxxxx>]

On 3/1/22 15:36, Maxim Levitsky wrote:
> @@ -565,8 +565,19 @@ static void nested_vmcb02_prepare_save(struct vcpu_svm *svm, struct vmcb *vmcb12
>   		vmcb_mark_dirty(svm->vmcb, VMCB_DR);
>   	}
>   
> -	if (unlikely(svm->vmcb01.ptr->control.virt_ext & LBR_CTL_ENABLE_MASK))
> +	if (unlikely(svm->lbrv_enabled && (svm->nested.ctl.virt_ext & LBR_CTL_ENABLE_MASK))) {
> +
> +		/* Copy LBR related registers from vmcb12,
> +		 * but make sure that we only pick LBR enable bit from the guest.
> +		 */
> +
> +		svm_copy_lbrs(vmcb12, svm->vmcb);
> +		svm->vmcb->save.dbgctl &= LBR_CTL_ENABLE_MASK;

This should be checked against DEBUGCTL_RESERVED_BITS instead in 
__nested_vmcb_check_save; remember to add dbgctl to struct 
vmcb_save_area_cached too.

Paolo

> +		svm_update_lbrv(&svm->vcpu);
> +
> +	} else if (unlikely(svm->vmcb01.ptr->control.virt_ext & LBR_CTL_ENABLE_MASK)) {
>   		svm_copy_lbrs(svm->vmcb01.ptr, svm->vmcb);
> +	}
>   }