From: Paolo Bonzini <pbonzini@redhat.com>
To: Eric Northup <digitaleric@google.com>, jingqi.liu@intel.com
Cc: rkrcmar@redhat.com, Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
bp@alien8.de, "H. Peter Anvin" <hpa@zytor.com>,
the arch/x86 maintainers <x86@kernel.org>,
KVM <kvm@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
tao3.xu@intel.com
Subject: Re: [PATCH v2 0/2] KVM: x86: expose direct stores instructions into VM.
Date: Wed, 30 Jan 2019 18:15:41 +0100 [thread overview]
Message-ID: <d3c7edcb-0499-182b-acda-c5f1f4d4e7b3@redhat.com> (raw)
In-Reply-To: <CAG7+5M0XNw6KOTw6JyqT67fp3cAX=MseT1A0_1Zpb6UM_O3fLw@mail.gmail.com>
On 30/11/18 21:41, Eric Northup wrote:
> On Mon, Nov 5, 2018 at 10:01 PM Liu Jingqi <jingqi.liu@intel.com> 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.
Paolo
next prev parent reply other threads:[~2019-01-30 17:15 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-06 5:55 [PATCH v2 0/2] KVM: x86: expose direct stores instructions into VM Liu Jingqi
2018-11-06 5:55 ` [PATCH v2 1/2] KVM: x86: expose MOVDIRI CPU feature " Liu Jingqi
2018-11-06 5:55 ` [PATCH v2 2/2] KVM: x86: expose MOVDIR64B " Liu Jingqi
2018-11-29 10:13 ` [PATCH v2 0/2] KVM: x86: expose direct stores instructions " David Hildenbrand
2018-11-30 20:41 ` Eric Northup
2019-01-30 17:15 ` Paolo Bonzini [this message]
2019-01-30 17:16 ` Paolo Bonzini
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