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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id c9sm3230863edt.6.2021.02.25.02.15.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 25 Feb 2021 02:15:21 -0800 (PST) Subject: Re: [PATCH] KVM: SVM: Fix nested VM-Exit on #GP interception handling To: Sean Christopherson Cc: Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210224005627.657028-1-seanjc@google.com> From: Paolo Bonzini Message-ID: <3cd45ce5-fde0-eda1-9797-66d7d5212bd9@redhat.com> Date: Thu, 25 Feb 2021 11:15:20 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <20210224005627.657028-1-seanjc@google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 24/02/21 01:56, Sean Christopherson wrote: > Fix the interpreation of nested_svm_vmexit()'s return value when > synthesizing a nested VM-Exit after intercepting an SVM instruction while > L2 was running. The helper returns '0' on success, whereas a return > value of '0' in the exit handler path means "exit to userspace". The > incorrect return value causes KVM to exit to userspace without filling > the run state, e.g. QEMU logs "KVM: unknown exit, hardware reason 0". > > Fixes: 14c2bf81fcd2 ("KVM: SVM: Fix #GP handling for doubly-nested virtualization") > Signed-off-by: Sean Christopherson > --- > arch/x86/kvm/svm/svm.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > index 14e41dddc7eb..c4f2f2f6b945 100644 > --- a/arch/x86/kvm/svm/svm.c > +++ b/arch/x86/kvm/svm/svm.c > @@ -2200,13 +2200,18 @@ static int emulate_svm_instr(struct kvm_vcpu *vcpu, int opcode) > [SVM_INSTR_VMSAVE] = vmsave_interception, > }; > struct vcpu_svm *svm = to_svm(vcpu); > + int ret; > > if (is_guest_mode(vcpu)) { > svm->vmcb->control.exit_code = guest_mode_exit_codes[opcode]; > svm->vmcb->control.exit_info_1 = 0; > svm->vmcb->control.exit_info_2 = 0; > > - return nested_svm_vmexit(svm); > + /* Returns '1' or -errno on failure, '0' on success. */ > + ret = nested_svm_vmexit(svm); > + if (ret) > + return ret; > + return 1; > } > return svm_instr_handlers[opcode](vcpu); > } > Queued, thanks. Paolo