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Date: Thu, 23 Sep 2021 18:44:48 +0200 From: Paolo Bonzini <pbonzini@...hat.com> To: Maxim Levitsky <mlevitsk@...hat.com>, kvm@...r.kernel.org Cc: Vitaly Kuznetsov <vkuznets@...hat.com>, Borislav Petkov <bp@...en8.de>, Bandan Das <bsd@...hat.com>, open list <linux-kernel@...r.kernel.org>, Joerg Roedel <joro@...tes.org>, Ingo Molnar <mingo@...hat.com>, Wei Huang <wei.huang2@....com>, Sean Christopherson <seanjc@...gle.com>, "open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@...r.kernel.org>, "H. Peter Anvin" <hpa@...or.com>, Jim Mattson <jmattson@...gle.com>, Thomas Gleixner <tglx@...utronix.de>, "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>, Shuah Khan <shuah@...nel.org>, Wanpeng Li <wanpengli@...cent.com> Subject: Re: [PATCH 07/14] KVM: x86: SVM: add warning for CVE-2021-3656 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 <mlevitsk@...hat.com> > --- > 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
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