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[91.219.240.2]) by smtp.gmail.com with ESMTPSA id l15sm2777902wrt.81.2020.09.01.07.55.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Sep 2020 07:55:49 -0700 (PDT) From: Vitaly Kuznetsov To: kvm@vger.kernel.org Cc: Sean Christopherson , Wanpeng Li , Jim Mattson , Eduardo Habkost , Jon Doron , linux-kernel@vger.kernel.org, Paolo Bonzini Subject: Re: [PATCH 0/7] KVM: x86: hyper-v: make KVM_GET_SUPPORTED_HV_CPUID more useful In-Reply-To: <20200807083946.377654-1-vkuznets@redhat.com> References: <20200807083946.377654-1-vkuznets@redhat.com> Date: Tue, 01 Sep 2020 16:55:48 +0200 Message-ID: <87blipwnpn.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Vitaly Kuznetsov writes: > KVM_GET_SUPPORTED_HV_CPUID was initially implemented as a vCPU ioctl but > this is not very useful when VMM is just trying to query which Hyper-V > features are supported by the host prior to creating VM/vCPUs. The data > in KVM_GET_SUPPORTED_HV_CPUID is mostly static with a few exceptions but > it seems we can change this. Add support for KVM_GET_SUPPORTED_HV_CPUID as > a system ioctl as well. > > QEMU specific description: > In some cases QEMU needs to collect the information about which Hyper-V > features are supported by KVM and pass it up the stack. For non-hyper-v > features this is done with system-wide KVM_GET_SUPPORTED_CPUID/ > KVM_GET_MSRS ioctls but Hyper-V specific features don't get in the output > (as Hyper-V CPUIDs intersect with KVM's). In QEMU, CPU feature expansion > happens before any KVM vcpus are created so KVM_GET_SUPPORTED_HV_CPUID > can't be used in its current shape. > Ping ;-) I know Hyper-V emulation in KVM is a very specific topic so it's not very easy to find reviewers but I'd be very happy if someone could provide any feedback on the idea (above) in general. -- Vitaly