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AL+hErHRIwD1ePFR5859ys2alGO54CW2Zn9i96xYyq9p4x3x0IrofSoQK065pGgQ1WZLm4B/j3Zod64ZTaf1Bew=@vger.kernel.org X-Gm-Message-State: APuU4Z9t5ZetJ0ctn9EK8ov/G/gPEJhWHUpboDieJ0e/4HjWtk2OXxuU nZrCW5bBfbAuacjSO/aA3ebGr4ObiEjZcVPa+Hez6TszWRY9zGL2AmVWakOsyojsf3QpHModDDT 0bVYd+TSfbTun3w== X-Received: from iogk24-n2.prod.google.com ([2002:a05:6602:c498:20b0:9c7:b2b5:20af]) (user=jmattson job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6808:250d:b0:567:cbf5:bb96 with SMTP id 5614622812f47-5683cac433dmr906887b6e.44.1794271241975; Mon, 09 Nov 2026 16:40:41 -0800 (PST) Date: Mon, 9 Nov 2026 16:40:37 -0800 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list Mime-Version: 1.0 X-Mailer: git-send-email 2.56.0.506.g506a7eabc5-goog Message-ID: <20261110004037.125692-1-jmattson@google.com> Subject: [PATCH] KVM: nSVM: Add missing CET VMRUN consistency checks From: Jim Mattson To: Sean Christopherson , Paolo Bonzini Cc: John Allen , Chao Gao , Yosry Ahmed , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Jim Mattson Content-Type: text/plain; charset="UTF-8" Per the APM, "Canonicalization and Consistency Checks," [t]he following conditions are considered illegal state combinations: - CR4.CET=1 when CR0.WP=0 - Any reserved bit set in S_CET - CR4.CET=1 and U_CET.SS=1 when EFLAGS.VM=1 Check these conditions in software before trying to VMRUN vmcb02, so that the illegal states result in a #VMEXIT to L1 rather than an exit to userspace with KVM_EXIT_FAIL_ENTRY. Fixes: c5ba49458513 ("KVM: nSVM: Save/load CET Shadow Stack state to/from vmcb12/vmcb02") Signed-off-by: Jim Mattson --- arch/x86/kvm/svm/nested.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index af0ef678433d..20ede403b62d 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -469,6 +469,21 @@ static bool nested_vmcb_check_save(struct kvm_vcpu *vcpu, if (CC(!__kvm_is_valid_cr4(vcpu, save->cr4))) return false; + if (CC((save->cr4 & X86_CR4_CET) && !(save->cr0 & X86_CR0_WP))) + return false; + + if (guest_cpu_cap_has(vcpu, X86_FEATURE_SHSTK) && + CC(!kvm_is_valid_u_s_cet(vcpu, save->s_cet))) + return false; + + if ((save->cr4 & X86_CR4_CET) && (save->rflags & X86_EFLAGS_VM)) { + u64 u_cet = 0; + + if (!__kvm_emulate_msr_read(vcpu, MSR_IA32_U_CET, &u_cet) && + CC(u_cet & CET_SHSTK_EN)) + return false; + } + if (CC(!kvm_valid_efer(vcpu, save->efer))) return false; -- 2.56.0.506.g506a7eabc5-goog