Re: [PATCH] Ignore DEBUGCTL MSRs

[Alexander Graf <agraf@suse.de>]

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Avi Kivity wrote:
> Alexander Graf wrote:
>> Netware writes and reads to the DEBUGCTL and LAST*IP MSRs without 
>> further checks and is really confused to receive a #GP during that. 
>> To make it happy we should just make them stubs, which is exactly 
>> what SVM already does.
>>
>> To support VMX too, I put these in the generic code. Maybe the SVM 
>> code could be cleaned up to use generic code too.
>>
>
> Please add a pr_unimpl() when bits that cause a real processor to do 
> something are set.

Like this? I also removed the set handlers for the *IP MSRs, as these 
are read only and made it only handle debug bits, no perfmon bits.

Signed-off-by: Alexander Graf <agraf@suse.de>



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diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fc0721e..10f5e95 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -609,6 +609,15 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 		pr_unimpl(vcpu, "%s: MSR_IA32_MCG_CTL 0x%llx, nop\n",
 			__func__, data);
 		break;
+	case MSR_IA32_DEBUGCTLMSR:
+		if (data > (DEBUGCTLMSR_LBR | DEBUGCTLMSR_BTF)) {
+			/* Values other than LBR and BTF are vendor-specific,
+			   thus reserved and should throw a #GP */
+			return 1;
+		}
+		pr_unimpl(vcpu, "%s: MSR_IA32_DEBUGCTLMSR 0x%llx, nop\n",
+			__func__, data);
+		break;
 	case MSR_IA32_UCODE_REV:
 	case MSR_IA32_UCODE_WRITE:
 		break;
@@ -705,6 +714,11 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
 	case MSR_IA32_MC0_MISC+16:
 	case MSR_IA32_UCODE_REV:
 	case MSR_IA32_EBL_CR_POWERON:
+	case MSR_IA32_DEBUGCTLMSR:
+	case MSR_IA32_LASTBRANCHFROMIP:
+	case MSR_IA32_LASTBRANCHTOIP:
+	case MSR_IA32_LASTINTFROMIP:
+	case MSR_IA32_LASTINTTOIP:
 		data = 0;
 		break;
 	case MSR_MTRRcap: