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Sun, 14 Jun 2026 20:33:48 -0700 (PDT) From: Saul Freedman To: qemu-devel@nongnu.org Cc: Saul Freedman , pbonzini@redhat.com, mtosatti@redhat.com, kvm@vger.kernel.org, qemu-stable@nongnu.org Subject: [PATCH] target/i386/kvm: Fix CET SSP MSR read feature check Date: Sun, 14 Jun 2026 23:33:38 -0400 Message-Id: <20260615033338.1563854-1-fre3dm4n@gmail.com> X-Mailer: git-send-email 2.39.5 MIME-Version: 1.0 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=2607:f8b0:4864:20::62d; envelope-from=fre3dm4n@gmail.com; helo=mail-pl1-x62d.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-Mailman-Approved-At: Mon, 15 Jun 2026 02:03:15 -0400 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 @gmail.com) X-ZM-MESSAGEID: 1781503445714158500 Content-Type: text/plain; charset="utf-8" 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 --- 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 9e35288..3f4a241 100644 --- a/target/i386/kvm/kvm.c +++ b/target/i386/kvm/kvm.c @@ -5021,7 +5021,7 @@ 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 2.39.5