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SubjectRe: [PATCH v2 0/2] KVM: x86: expose direct stores instructions into VM.
On 30/11/18 21:41, Eric Northup wrote:
> On Mon, Nov 5, 2018 at 10:01 PM Liu Jingqi <> wrote:
>> Direct stores instructions MOVDIRI and MOVDIR64B will be available in
>> Tremont and other future x86 processors,
>> and need to be exposed to guest VM.
> It seems like KVM's emulator should be able to complete these
> instructions to emulated MMIO before exposing CPUID to guests in any
> default or supported configurations.
> It'll be much simpler for usermode to implement that property if the
> KVM-reported supported CPUID table doesn't get updated before the KVM
> emulator does.

We already do not support emulation for many CPUID bits we expose (AVX
and AVX512 above all), so that's not a huge problem.

I suppose these instructions are unlikely to be used on MMIO areas such
as legacy VGA VRAM.


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