[PATCH] svm last branch recording MSR emulation

[PATCH] svm last branch recording MSR emulation

[Markus Rechberger]

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Hi,

this patch adds support for the lbr MSR emulation, it also enables 
support for Windows XP 64bit guests.

Signed-off-by: Joerg Roedel <Joerg.Roedel-5C7GfCeVMHo@public.gmane.org>
Signed-off-by: Markus Rechberger <Markus.Rechberger-5C7GfCeVMHo@public.gmane.org>


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--- svm.c.orig	2008-01-23 10:04:14.000000000 +0100
+++ svm.c	2008-01-25 12:52:11.000000000 +0100
@@ -1099,6 +1100,21 @@
 	case MSR_IA32_SYSENTER_ESP:
 		*data = svm->vmcb->save.sysenter_esp;
 		break;
+	case MSR_IA32_DEBUGCTLMSR:
+		*data = svm->vmcb->save.dbgctl;
+		break;
+	case MSR_IA32_LASTBRANCHFROMIP:
+		*data = svm->vmcb->save.br_from;
+		break;
+	case MSR_IA32_LASTBRANCHTOIP:
+		*data = svm->vmcb->save.br_to;
+		break;
+	case MSR_IA32_LASTINTFROMIP:
+		*data = svm->vmcb->save.last_excp_from;
+		break;
+	case MSR_IA32_LASTINTTOIP:
+		*data = svm->vmcb->save.last_excp_to;
+		break;
 	default:
 		return kvm_get_msr_common(vcpu, ecx, data);
 	}
@@ -1171,6 +1187,19 @@
 		if (data != 0)
 			goto unhandled;
 		break;
+	case MSR_IA32_DEBUGCTLMSR:
+		svm->vmcb->save.dbgctl = data;
+		if (svm->vmcb->save.dbgctl && svm_has(SVM_FEATURE_LBRV)) {
+			void *msrpm_va;
+			svm->vmcb->control.lbr_ctl = 1;
+			msrpm_va = page_address(pfn_to_page(msrpm_base >> PAGE_SHIFT));
+			set_msr_interception(msrpm_va, MSR_IA32_DEBUGCTLMSR, 0, 0);
+			set_msr_interception(msrpm_va, MSR_IA32_LASTBRANCHFROMIP, 0, 0);
+			set_msr_interception(msrpm_va, MSR_IA32_LASTBRANCHTOIP, 0, 0);
+			set_msr_interception(msrpm_va, MSR_IA32_LASTINTFROMIP, 0, 0);
+			set_msr_interception(msrpm_va, MSR_IA32_LASTINTTOIP, 0, 0);
+		}
+		break;
 	default:
 	unhandled:
 		return kvm_set_msr_common(vcpu, ecx, data);

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Re: [PATCH] svm last branch recording MSR emulation

[Avi Kivity]

Markus Rechberger wrote:
> this patch adds support for the lbr MSR emulation, it also enables 
> support for Windows XP 64bit guests.
>
> Signed-off-by: Joerg Roedel <Joerg.Roedel-5C7GfCeVMHo@public.gmane.org>
> Signed-off-by: Markus Rechberger <Markus.Rechberger-5C7GfCeVMHo@public.gmane.org>
> @@ -1171,6 +1187,19 @@
>  		if (data != 0)
>  			goto unhandled;
>  		break;
> +	case MSR_IA32_DEBUGCTLMSR:
> +		svm->vmcb->save.dbgctl = data;
> +		if (svm->vmcb->save.dbgctl && svm_has(SVM_FEATURE_LBRV)) {
> +			void *msrpm_va;
>   

blank line

> +			svm->vmcb->control.lbr_ctl = 1;
> +			msrpm_va = page_address(pfn_to_page(msrpm_base >> PAGE_SHIFT));
> +			set_msr_interception(msrpm_va, MSR_IA32_DEBUGCTLMSR, 0, 0);
> +			set_msr_interception(msrpm_va, MSR_IA32_LASTBRANCHFROMIP, 0, 0);
> +			set_msr_interception(msrpm_va, MSR_IA32_LASTBRANCHTOIP, 0, 0);
> +			set_msr_interception(msrpm_va, MSR_IA32_LASTINTFROMIP, 0, 0);
> +			set_msr_interception(msrpm_va, MSR_IA32_LASTINTTOIP, 0, 0);
> +		}
> +		break;
>  	default:
>  	unhandled:

What is the performance impact (for example, on 
user/test/x86/vmexit.flat when modified to set a bit in debugctl)?

Is it not better to enable LBR virtualization only when the guest 
enables LBR (but avoid it when other bits are enabled)?

Can we disable LBR virtualization when the guest disables LBR?

-- 
error compiling committee.c: too many arguments to function


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