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SubjectRe: [PATCH] KVM: x86: svm: report MSR_IA32_MCG_EXT_CTL as unsupported
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Radim Krčmář <rkrcmar@redhat.com> writes:

> 2018-12-19 12:06+0100, Vitaly Kuznetsov:
>> AMD doesn't seem to implement MSR_IA32_MCG_EXT_CTL and svm code in kvm
>> knows nothing about it, however, this MSR is among emulated_msrs and
>> thus returned with KVM_GET_MSR_INDEX_LIST. The consequent KVM_GET_MSRS,
>> of course, fails.
>>
>> Report the MSR as unsupported to not confuse userspace.
>>
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
>> ---
>> arch/x86/kvm/svm.c | 7 +++++++
>> 1 file changed, 7 insertions(+)
>>
>> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
>> index 2acb42b74a51..dfdf7d0b7f88 100644
>> --- a/arch/x86/kvm/svm.c
>> +++ b/arch/x86/kvm/svm.c
>> @@ -5845,6 +5845,13 @@ static bool svm_cpu_has_accelerated_tpr(void)
>>
>> static bool svm_has_emulated_msr(int index)
>> {
>> + switch (index) {
>> + case MSR_IA32_MCG_EXT_CTL:
>> + return false;
>> + default:
>> + break;
>
> Queued, thanks.
>
> Btw, I would prefer this without the
>
> default: break;
>
> as I don't think we'll ever add something there.

"640K ought to be enough for anybody" :-)

But in case you commit it as

return index != MSR_IA32_MCG_EXT_CTL;

I won't object. Thanks,

--
Vitaly

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