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([2001:b07:add:ec09:c399:bc87:7b6c:fb2a]) by smtp.gmail.com with ESMTPSA id la15sm7992488ejb.46.2021.03.15.10.56.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 15 Mar 2021 10:56:04 -0700 (PDT) Subject: Re: [PATCH 2/2] KVM: nSVM: improve SYSENTER emulation on AMD To: Maxim Levitsky , kvm@vger.kernel.org Cc: "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , "H. Peter Anvin" , Sean Christopherson , Ingo Molnar , Jim Mattson , Vitaly Kuznetsov , Joerg Roedel , Thomas Gleixner , "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , Wanpeng Li , Borislav Petkov References: <20210315174316.477511-1-mlevitsk@redhat.com> <20210315174316.477511-3-mlevitsk@redhat.com> From: Paolo Bonzini Message-ID: <0dbcff57-8197-8fbb-809d-b47a4f5e9e77@redhat.com> Date: Mon, 15 Mar 2021 18:56:00 +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: <20210315174316.477511-3-mlevitsk@redhat.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 15/03/21 18:43, Maxim Levitsky wrote: > + if (!guest_cpuid_is_intel(vcpu)) { > + /* > + * If hardware supports Virtual VMLOAD VMSAVE then enable it > + * in VMCB and clear intercepts to avoid #VMEXIT. > + */ > + if (vls) { > + svm_clr_intercept(svm, INTERCEPT_VMLOAD); > + svm_clr_intercept(svm, INTERCEPT_VMSAVE); > + svm->vmcb->control.virt_ext |= VIRTUAL_VMLOAD_VMSAVE_ENABLE_MASK; > + } > + /* No need to intercept these msrs either */ > + set_msr_interception(vcpu, svm->msrpm, MSR_IA32_SYSENTER_EIP, 1, 1); > + set_msr_interception(vcpu, svm->msrpm, MSR_IA32_SYSENTER_ESP, 1, 1); > + } An "else" is needed here to do the opposite setup (removing the "if (vls)" from init_vmcb). This also makes the code more readable since you can write if (guest_cpuid_is_intel(vcpu)) { /* * We must intercept SYSENTER_EIP and SYSENTER_ESP * accesses because the processor only stores 32 bits. * For the same reason we cannot use virtual * VMLOAD/VMSAVE. */ ... } else { /* Do the opposite. */ ... } Paolo