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[213.175.37.10]) by smtp.gmail.com with ESMTPSA id v22sm22281449wml.11.2020.01.20.08.33.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Jan 2020 08:33:27 -0800 (PST) From: Vitaly Kuznetsov To: Paolo Bonzini Cc: Jim Mattson , Sean Christopherson , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Liran Alon Subject: Re: [RFC] Revert "kvm: nVMX: Restrict VMX capability MSR changes" In-Reply-To: <30525d58-10de-abb4-8dad-228da766ff82@redhat.com> References: <20200120151141.227254-1-vkuznets@redhat.com> <30525d58-10de-abb4-8dad-228da766ff82@redhat.com> Date: Mon, 20 Jan 2020 17:33:26 +0100 Message-ID: <87k15mf5pl.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 Paolo Bonzini writes: > On 20/01/20 16:11, Vitaly Kuznetsov wrote: >> >> RFC. I think the check for vmx->nested.vmxon is legitimate for everything >> but restore so removing it (what I do with the revert) is likely a no-go. >> I'd like to gather opinions on the proper fix: should we somehow check >> that the vCPU is in 'restore' start (has never being run) and make >> KVM_SET_MSRS pass or should we actually mandate that KVM_SET_NESTED_STATE >> is run after KVM_SET_MSRS by userspace? >> >> Signed-off-by: Vitaly Kuznetsov > > I think this should be fixed in QEMU, by doing KVM_SET_MSRS for feature > MSRs way earlier. I'll do it since I'm currently working on a patch to > add a KVM_SET_MSR for the microcode revision. Works for me, thanks) The bigger issue is that the vCPU setup sequence (like QEMU's kvm_arch_put_registers()) effectively becomes an API convention and as it gets more complex it would be great to document it for KVM. -- Vitaly