linux-kernel - [PATCH v12 12/24] KVM: x86: Report KVM supported CET MSRs as to-be-saved

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Message-ID: <20250812025606.74625-13-chao.gao@intel.com>
Date: Mon, 11 Aug 2025 19:55:20 -0700
From: Chao Gao <chao.gao@...el.com>
To: kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: mlevitsk@...hat.com,
	rick.p.edgecombe@...el.com,
	weijiang.yang@...el.com,
	xin@...or.com,
	Chao Gao <chao.gao@...el.com>,
	Mathias Krause <minipli@...ecurity.net>,
	John Allen <john.allen@....com>,
	Sean Christopherson <seanjc@...gle.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH v12 12/24] KVM: x86: Report KVM supported CET MSRs as to-be-saved

From: Yang Weijiang <weijiang.yang@...el.com>

Add CET MSRs to the list of MSRs reported to userspace if the feature,
i.e. IBT or SHSTK, associated with the MSRs is supported by KVM.

Suggested-by: Chao Gao <chao.gao@...el.com>
Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
Tested-by: Mathias Krause <minipli@...ecurity.net>
Tested-by: John Allen <john.allen@....com>
Signed-off-by: Chao Gao <chao.gao@...el.com>
---
 arch/x86/kvm/x86.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index cca05908f989..7134f428b9f7 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -341,6 +341,10 @@ static const u32 msrs_to_save_base[] = {
 	MSR_IA32_UMWAIT_CONTROL,
 
 	MSR_IA32_XFD, MSR_IA32_XFD_ERR, MSR_IA32_XSS,
+
+	MSR_IA32_U_CET, MSR_IA32_S_CET,
+	MSR_IA32_PL0_SSP, MSR_IA32_PL1_SSP, MSR_IA32_PL2_SSP,
+	MSR_IA32_PL3_SSP, MSR_IA32_INT_SSP_TAB,
 };
 
 static const u32 msrs_to_save_pmu[] = {
@@ -7490,6 +7494,20 @@ static void kvm_probe_msr_to_save(u32 msr_index)
 		if (!kvm_caps.supported_xss)
 			return;
 		break;
+	case MSR_IA32_U_CET:
+	case MSR_IA32_S_CET:
+		if (!kvm_cpu_cap_has(X86_FEATURE_SHSTK) &&
+		    !kvm_cpu_cap_has(X86_FEATURE_IBT))
+			return;
+		break;
+	case MSR_IA32_INT_SSP_TAB:
+		if (!kvm_cpu_cap_has(X86_FEATURE_LM))
+			return;
+		fallthrough;
+	case MSR_IA32_PL0_SSP ... MSR_IA32_PL3_SSP:
+		if (!kvm_cpu_cap_has(X86_FEATURE_SHSTK))
+			return;
+		break;
 	default:
 		break;
 	}
-- 
2.47.1