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([2001:b07:6468:f312:c6d:4079:b74c:e329]) by smtp.gmail.com with ESMTPSA id a184sm27055593wmf.29.2020.01.07.04.25.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 07 Jan 2020 04:25:28 -0800 (PST) Subject: Re: [PATCH RFC] i386/kvm: fix enlightened VMCS with fine-grained VMX feature enablement To: Vitaly Kuznetsov , qemu-devel@nongnu.org References: <20200102203926.1179743-1-vkuznets@redhat.com> <21556857-3d6a-ad66-5cf5-060b1ab67381@redhat.com> <87zhezsc30.fsf@vitty.brq.redhat.com> From: Paolo Bonzini Message-ID: <7c4dcca1-a1e6-a00c-56fd-bcc6c8bcc474@redhat.com> Date: Tue, 7 Jan 2020 13:25:27 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <87zhezsc30.fsf@vitty.brq.redhat.com> Content-Language: en-US X-MC-Unique: RZZyHPMKPueydl1nvPbe2g-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Roman Kagan , Marcelo Tosatti , Liran Alon , Eduardo Habkost , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 07/01/20 13:08, Vitaly Kuznetsov wrote: > Honestly I forgot the story why we filtered out these features upon > eVMCS enablement in KVM. As there are no corresponding eVMCS fields, > there's no way a guest can actually use them. Well, mostly because we mimicked what Hyper-V was doing I guess. > I'm going to check that nothing breaks if we remove the filter. I'll go > and test Hyper-V 2016 and 2019. KVM would break, right? But we can mark that patch as stable material. Paolo >> If so, we should teach guest-side KVM about this, not QEMU. > > This is not required when enabling eVMCS on a genuine Hyper-V because it > correctly filters out unsupported features, however, to not break > KVM-on-KVM-using-eVMCS case we'll have to move the filter from host to > guest. > > Thanks! >