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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id g9sm3414971ejo.60.2021.09.23.09.44.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 23 Sep 2021 09:44:51 -0700 (PDT) Subject: Re: [PATCH 07/14] KVM: x86: SVM: add warning for CVE-2021-3656 To: Maxim Levitsky , kvm@vger.kernel.org Cc: Vitaly Kuznetsov , Borislav Petkov , Bandan Das , open list , Joerg Roedel , Ingo Molnar , Wei Huang , Sean Christopherson , "open list:KERNEL SELFTEST FRAMEWORK" , "H. Peter Anvin" , Jim Mattson , Thomas Gleixner , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , Shuah Khan , Wanpeng Li References: <20210914154825.104886-1-mlevitsk@redhat.com> <20210914154825.104886-8-mlevitsk@redhat.com> From: Paolo Bonzini Message-ID: Date: Thu, 23 Sep 2021 18:44:48 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210914154825.104886-8-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 14/09/21 17:48, Maxim Levitsky wrote: > Just in case, add a warning ensuring that on guest entry, > either both VMLOAD and VMSAVE intercept is enabled or > vVMLOAD/VMSAVE is enabled. > > Signed-off-by: Maxim Levitsky > --- > arch/x86/kvm/svm/svm.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > index 861ac9f74331..deeebd05f682 100644 > --- a/arch/x86/kvm/svm/svm.c > +++ b/arch/x86/kvm/svm/svm.c > @@ -3784,6 +3784,12 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu) > > WARN_ON_ONCE(kvm_apicv_activated(vcpu->kvm) != kvm_vcpu_apicv_active(vcpu)); > > + /* Check that CVE-2021-3656 can't happen again */ > + if (!svm_is_intercept(svm, INTERCEPT_VMSAVE) || > + !svm_is_intercept(svm, INTERCEPT_VMSAVE)) > + WARN_ON(!(svm->vmcb->control.virt_ext & > + VIRTUAL_VMLOAD_VMSAVE_ENABLE_MASK)); > + > sync_lapic_to_cr8(vcpu); > > if (unlikely(svm->asid != svm->vmcb->control.asid)) { > While it's nice to be "proactive", this does adds some extra work. Maybe it should be under CONFIG_DEBUG_KERNEL. It could be useful to make it into its own function so we can add similar intercept invariants in the same place. Paolo