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Fri, 07 Aug 2026 07:41:41 -0700 (PDT) X-Received: by 2002:a7b:c7d7:0:b0:495:4811:d71c with SMTP id 5b1f17b1804b1-4994e7c55bcmr266965725e9.13.1786113701322; Fri, 07 Aug 2026 07:41:41 -0700 (PDT) From: Paolo Bonzini To: qemu-devel@nongnu.org Cc: Saul Freedman , qemu-stable@nongnu.org, =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= Subject: [PULL 1/1] target/i386/kvm: Fix CET SSP MSR read feature check Date: Fri, 7 Aug 2026 16:41:36 +0200 Message-ID: <20260807144136.2637416-2-pbonzini@redhat.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260807144136.2637416-1-pbonzini@redhat.com> References: <20260807144136.2637416-1-pbonzini@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists1p.gnu.org; Received-SPF: pass client-ip=170.10.129.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -32 X-Spam_score: -3.3 X-Spam_bar: --- X-Spam_report: (-3.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.238, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1786113782031158500 From: Saul Freedman kvm_get_msrs() adds U_CET and S_CET when CET shadow stacks or IBT are enabled, but it checks FEAT_7_0_EDX with the ECX-defined CPUID_7_0_ECX_CET_SHSTK bit before adding the PL0-PL3 SSP MSRs. CPUID_7_0_ECX_CET_SHSTK belongs to FEAT_7_0_ECX. The current check therefore skips MSR_IA32_PL0_SSP through MSR_IA32_PL3_SSP even when guest shadow stacks are enabled. kvm_put_msrs() already uses FEAT_7_0_ECX for the same shadow-stack condition. Use the same feature word in kvm_get_msrs() so QEMU does not restore CET enablement with stale or zero SSP values. Fixes: b6f85c5e4527 ("i386/kvm: Add save/restore support for CET MSRs") Cc: qemu-stable@nongnu.org Signed-off-by: Saul Freedman Reviewed-by: Philippe Mathieu-Daud=C3=A9 Link: https://lore.kernel.org/r/20260615033338.1563854-1-fre3dm4n@gmail.com Signed-off-by: Paolo Bonzini --- target/i386/kvm/kvm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c index 4272b6770c7..644c45fb0a0 100644 --- a/target/i386/kvm/kvm.c +++ b/target/i386/kvm/kvm.c @@ -5022,7 +5022,7 @@ static int kvm_get_msrs(X86CPU *cpu) kvm_msr_entry_add(cpu, MSR_IA32_U_CET, 0); kvm_msr_entry_add(cpu, MSR_IA32_S_CET, 0); =20 - if (env->features[FEAT_7_0_EDX] & CPUID_7_0_ECX_CET_SHSTK) { + if (env->features[FEAT_7_0_ECX] & CPUID_7_0_ECX_CET_SHSTK) { kvm_msr_entry_add(cpu, MSR_IA32_PL0_SSP, 0); kvm_msr_entry_add(cpu, MSR_IA32_PL1_SSP, 0); kvm_msr_entry_add(cpu, MSR_IA32_PL2_SSP, 0); --=20 2.55.0