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Fri, 12 Sep 2025 15:04:11 -0700 (PDT) Date: Fri, 12 Sep 2025 15:04:09 -0700 In-Reply-To: <20250909093953.202028-15-chao.gao@intel.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250909093953.202028-1-chao.gao@intel.com> <20250909093953.202028-15-chao.gao@intel.com> Message-ID: Subject: Re: [PATCH v14 14/22] KVM: VMX: Set host constant supervisor states to VMCS fields From: Sean Christopherson To: Chao Gao Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, acme@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, john.allen@amd.com, mingo@kernel.org, mingo@redhat.com, minipli@grsecurity.net, mlevitsk@redhat.com, namhyung@kernel.org, pbonzini@redhat.com, prsampat@amd.com, rick.p.edgecombe@intel.com, shuah@kernel.org, tglx@linutronix.de, weijiang.yang@intel.com, x86@kernel.org, xin@zytor.com, xiaoyao.li@intel.com Content-Type: text/plain; charset="us-ascii" On Tue, Sep 09, 2025, Chao Gao wrote: > void set_cr4_guest_host_mask(struct vcpu_vmx *vmx) > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 79861b7ad44d..d67aef261638 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -9890,6 +9890,18 @@ int kvm_x86_vendor_init(struct kvm_x86_init_ops *ops) > return -EIO; > } > > + if (boot_cpu_has(X86_FEATURE_SHSTK)) { This needs to check for "|| IBT" > + rdmsrq(MSR_IA32_S_CET, kvm_host.s_cet); > + /* > + * Linux doesn't yet support supervisor shadow stacks (SSS), so > + * KVM doesn't save/restore the associated MSRs, i.e. KVM may > + * clobber the host values. Yell and refuse to load if SSS is > + * unexpectedly enabled, e.g. to avoid crashing the host. > + */ > + if (WARN_ON_ONCE(kvm_host.s_cet & CET_SHSTK_EN)) > + return -EIO; > + }