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[149.6.153.187]) by smtp.gmail.com with ESMTPSA id z8sm15809068wrq.22.2019.12.06.03.30.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 06 Dec 2019 03:30:50 -0800 (PST) Subject: Re: [PATCH] target/i386: skip kvm_msr_entry_add when kvm_vmx_basic is 0 To: Catherine Ho , Marcelo Tosatti , qemu-devel@nongnu.org References: <3a1c97b2-789f-dd21-59ba-f780cf3bad92@redhat.com> <1575627817-24625-1-git-send-email-catherine.hecx@gmail.com> From: Paolo Bonzini Message-ID: <9c86f277-f13c-b33d-41e5-0ed32aaf75d7@redhat.com> Date: Fri, 6 Dec 2019 12:30:48 +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: <1575627817-24625-1-git-send-email-catherine.hecx@gmail.com> Content-Language: en-US X-MC-Unique: jmcVBZMXM4S74h31T6UxTw-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.120 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: "Zhong, Yang" , Eduardo Habkost , kvm@vger.kernel.org, Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 06/12/19 11:23, Catherine Ho wrote: > Commit 1389309c811b ("KVM: nVMX: expose VMX capabilities for nested > hypervisors to userspace") expands the msr_based_features with > MSR_IA32_VMX_BASIC and others. Then together with an old kernel before > 1389309c811b, the qemu call KVM_GET_MSR_FEATURE_INDEX_LIST and got the > smaller kvm_feature_msrs. Then in kvm_arch_get_supported_msr_feature(), > searching VMX_BASIC will be failed and return 0. At last kvm_vmx_basic > will be assigned to 0. > > Without this patch, it will cause a qemu crash (host kernel 4.15 > ubuntu 18.04+qemu 4.1): > qemu-system-x86_64: error: failed to set MSR 0x480 to 0x0 > target/i386/kvm.c:2932: kvm_put_msrs: Assertion `ret == > cpu->kvm_msr_buf->nmsrs' failed. > > This fixes it by skipping kvm_msr_entry_add when kvm_vmx_basic is 0 > > Cc: Paolo Bonzini > Signed-off-by: Catherine Ho > --- > target/i386/kvm.c | 7 ++++++- > 1 files changed, 6 insertions(+), 1 deletions(-) > > diff --git a/target/i386/kvm.c b/target/i386/kvm.c > index a8c44bf..8cf84a2 100644 > --- a/target/i386/kvm.c > +++ b/target/i386/kvm.c > @@ -2632,8 +2632,13 @@ static void kvm_msr_entry_add_vmx(X86CPU *cpu, FeatureWordArray f) > f[FEAT_VMX_SECONDARY_CTLS])); > kvm_msr_entry_add(cpu, MSR_IA32_VMX_EPT_VPID_CAP, > f[FEAT_VMX_EPT_VPID_CAPS] | fixed_vmx_ept_vpid); > - kvm_msr_entry_add(cpu, MSR_IA32_VMX_BASIC, > + > + if (kvm_vmx_basic) { > + /* Only add the entry when host supports it */ > + kvm_msr_entry_add(cpu, MSR_IA32_VMX_BASIC, > f[FEAT_VMX_BASIC] | fixed_vmx_basic); > + } > + > kvm_msr_entry_add(cpu, MSR_IA32_VMX_MISC, > f[FEAT_VMX_MISC] | fixed_vmx_misc); > if (has_msr_vmx_vmfunc) { > Yang Zhong from Intel also sent a similar patch. Thanks very much to both of you. Paolo