From: Chao Gao <chao.gao@intel.com>
To: Xiaoyao Li <xiaoyao.li@intel.com>
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>, <seanjc@google.com>,
<shuah@kernel.org>, <tglx@linutronix.de>,
<weijiang.yang@intel.com>, <x86@kernel.org>, <xin@zytor.com>
Subject: Re: [PATCH v14 15/22] KVM: x86: Don't emulate instructions guarded by CET
Date: Thu, 11 Sep 2025 18:42:17 +0800 [thread overview]
Message-ID: <aMKniY+GguBPe8tK@intel.com> (raw)
In-Reply-To: <8121026d-aede-4f78-a081-b81186b96e9b@intel.com>
>> @@ -4941,6 +4947,24 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len, int
>> if (ctxt->d == 0)
>> return EMULATION_FAILED;
>> + if (ctxt->ops->get_cr(ctxt, 4) & X86_CR4_CET) {
>> + u64 u_cet, s_cet;
>> + bool stop_em;
>> +
>> + if (ctxt->ops->get_msr(ctxt, MSR_IA32_U_CET, &u_cet) ||
>> + ctxt->ops->get_msr(ctxt, MSR_IA32_S_CET, &s_cet))
>> + return EMULATION_FAILED;
>> +
>> + stop_em = ((u_cet & CET_SHSTK_EN) || (s_cet & CET_SHSTK_EN)) &&
>> + (opcode.flags & ShadowStack);
>> +
>> + stop_em |= ((u_cet & CET_ENDBR_EN) || (s_cet & CET_ENDBR_EN)) &&
>> + (opcode.flags & IndirBrnTrk);
>
>Why don't check CPL here? Just for simplicity?
I think so. This is a corner case and we don't want to make it very precise
(and thus complex). The reason is that no one had a strong opinion on whether
to do the CPL check or not. I asked the same question before [*], but I don't
have a strong opinion on this either.
[*]: https://lore.kernel.org/kvm/ZaSQn7RCRTaBK1bc@chao-email/
next prev parent reply other threads:[~2025-09-11 10:42 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-09 9:39 [PATCH v14 00/22] Enable CET Virtualization Chao Gao
2025-09-09 9:39 ` [PATCH v14 01/22] KVM: x86: Introduce KVM_{G,S}ET_ONE_REG uAPIs support Chao Gao
2025-09-10 9:03 ` Xiaoyao Li
2025-09-10 17:17 ` Sean Christopherson
2025-09-10 17:35 ` Sean Christopherson
2025-09-09 9:39 ` [PATCH v14 02/22] KVM: x86: Report XSS as to-be-saved if there are supported features Chao Gao
2025-09-11 6:52 ` Binbin Wu
2025-09-09 9:39 ` [PATCH v14 03/22] KVM: x86: Check XSS validity against guest CPUIDs Chao Gao
2025-09-10 9:22 ` Xiaoyao Li
2025-09-10 11:33 ` Chao Gao
2025-09-10 18:47 ` Sean Christopherson
2025-09-09 9:39 ` [PATCH v14 04/22] KVM: x86: Refresh CPUID on write to guest MSR_IA32_XSS Chao Gao
2025-09-10 9:23 ` Xiaoyao Li
2025-09-11 7:02 ` Binbin Wu
2025-09-09 9:39 ` [PATCH v14 05/22] KVM: x86: Initialize kvm_caps.supported_xss Chao Gao
2025-09-10 9:36 ` Xiaoyao Li
2025-09-09 9:39 ` [PATCH v14 06/22] KVM: x86: Load guest FPU state when access XSAVE-managed MSRs Chao Gao
2025-09-10 9:37 ` Xiaoyao Li
2025-09-10 11:18 ` Chao Gao
2025-09-10 13:46 ` Xiaoyao Li
2025-09-10 15:24 ` Chao Gao
2025-09-10 17:50 ` Sean Christopherson
2025-09-09 9:39 ` [PATCH v14 07/22] KVM: x86: Add fault checks for guest CR4.CET setting Chao Gao
2025-09-10 9:38 ` Xiaoyao Li
2025-09-09 9:39 ` [PATCH v14 08/22] KVM: x86: Report KVM supported CET MSRs as to-be-saved Chao Gao
2025-09-09 9:39 ` [PATCH v14 09/22] KVM: VMX: Introduce CET VMCS fields and control bits Chao Gao
2025-09-09 9:39 ` [PATCH v14 10/22] KVM: x86: Enable guest SSP read/write interface with new uAPIs Chao Gao
2025-09-09 9:39 ` [PATCH v14 11/22] KVM: VMX: Emulate read and write to CET MSRs Chao Gao
2025-09-11 8:05 ` Xiaoyao Li
2025-09-11 9:02 ` Chao Gao
2025-09-11 20:24 ` Sean Christopherson
2025-09-09 9:39 ` [PATCH v14 12/22] KVM: x86: Save and reload SSP to/from SMRAM Chao Gao
2025-09-09 9:39 ` [PATCH v14 13/22] KVM: VMX: Set up interception for CET MSRs Chao Gao
2025-09-09 9:39 ` [PATCH v14 14/22] KVM: VMX: Set host constant supervisor states to VMCS fields Chao Gao
2025-09-12 22:04 ` Sean Christopherson
2025-09-09 9:39 ` [PATCH v14 15/22] KVM: x86: Don't emulate instructions guarded by CET Chao Gao
2025-09-11 9:18 ` Xiaoyao Li
2025-09-11 10:42 ` Chao Gao [this message]
2025-09-12 6:23 ` Xiaoyao Li
2025-09-12 14:37 ` Sean Christopherson
2025-09-12 15:11 ` Sean Christopherson
2025-09-16 14:42 ` Chao Gao
2025-09-12 14:42 ` Sean Christopherson
2025-09-09 9:39 ` [PATCH v14 16/22] KVM: x86: Enable CET virtualization for VMX and advertise to userspace Chao Gao
2025-09-09 9:39 ` [PATCH v14 17/22] KVM: nVMX: Virtualize NO_HW_ERROR_CODE_CC for L1 event injection to L2 Chao Gao
2025-09-09 9:39 ` [PATCH v14 18/22] KVM: nVMX: Prepare for enabling CET support for nested guest Chao Gao
2025-09-09 9:39 ` [PATCH v14 19/22] KVM: nVMX: Add consistency checks for CR0.WP and CR4.CET Chao Gao
2025-09-09 9:39 ` [PATCH v14 20/22] KVM: nVMX: Add consistency checks for CET states Chao Gao
2025-09-09 9:39 ` [PATCH v14 21/22] KVM: nVMX: Advertise new VM-Entry/Exit control bits for CET state Chao Gao
2025-09-09 9:39 ` [PATCH v14 22/22] KVM: selftest: Add tests for KVM_{GET,SET}_ONE_REG Chao Gao
2025-09-10 18:06 ` Sean Christopherson
2025-09-09 9:52 ` [PATCH v14 00/22] Enable CET Virtualization Chao Gao
2025-09-10 18:29 ` Sean Christopherson
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