linux-kernel - [PATCH v15 36/41] KVM: selftests: Add support for MSR_IA32_{S,U}

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Message-ID: <20250912232319.429659-37-seanjc@google.com>
Date: Fri, 12 Sep 2025 16:23:14 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>, Sean Christopherson <seanjc@...gle.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Tom Lendacky <thomas.lendacky@....com>, Mathias Krause <minipli@...ecurity.net>, 
	John Allen <john.allen@....com>, Rick Edgecombe <rick.p.edgecombe@...el.com>, 
	Chao Gao <chao.gao@...el.com>, Maxim Levitsky <mlevitsk@...hat.com>, 
	Xiaoyao Li <xiaoyao.li@...el.com>, Zhang Yi Z <yi.z.zhang@...ux.intel.com>
Subject: [PATCH v15 36/41] KVM: selftests: Add support for MSR_IA32_{S,U}_CET
 to MSRs test

Extend the MSRs test to support {S,U}_CET, which are a bit of a pain to
handled due to the MSRs existing if IBT *or* SHSTK is supported.  To deal
with Intel's wonderful decision to bundle IBT and SHSTK under CET, track
the "second" feature and skip RDMSR #GP tests to avoid false failures when
running on a CPU with only one of IBT or SHSTK.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 tools/testing/selftests/kvm/x86/msrs_test.c | 22 ++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/kvm/x86/msrs_test.c b/tools/testing/selftests/kvm/x86/msrs_test.c
index dcb429cf1440..095d49d07235 100644
--- a/tools/testing/selftests/kvm/x86/msrs_test.c
+++ b/tools/testing/selftests/kvm/x86/msrs_test.c
@@ -11,6 +11,7 @@
 
 struct kvm_msr {
 	const struct kvm_x86_cpu_feature feature;
+	const struct kvm_x86_cpu_feature feature2;
 	const char *name;
 	const u64 reset_val;
 	const u64 write_val;
@@ -18,7 +19,7 @@ struct kvm_msr {
 	const u32 index;
 };
 
-#define __MSR_TEST(msr, str, val, rsvd, reset, feat)			\
+#define ____MSR_TEST(msr, str, val, rsvd, reset, feat, f2)		\
 {									\
 	.index = msr,							\
 	.name = str,							\
@@ -26,14 +27,21 @@ struct kvm_msr {
 	.rsvd_val = rsvd,						\
 	.reset_val = reset,						\
 	.feature = X86_FEATURE_ ##feat,					\
+	.feature2 = X86_FEATURE_ ##f2,					\
 }
 
+#define __MSR_TEST(msr, str, val, rsvd, reset, feat)			\
+	____MSR_TEST(msr, str, val, rsvd, reset, feat, feat)
+
 #define MSR_TEST_NON_ZERO(msr, val, rsvd, reset, feat)			\
 	__MSR_TEST(msr, #msr, val, rsvd, reset, feat)
 
 #define MSR_TEST(msr, val, rsvd, feat)					\
 	__MSR_TEST(msr, #msr, val, rsvd, 0, feat)
 
+#define MSR_TEST2(msr, val, rsvd, feat, f2)				\
+	____MSR_TEST(msr, #msr, val, rsvd, 0, feat, f2)
+
 /*
  * Note, use a page aligned value for the canonical value so that the value
  * is compatible with MSRs that use bits 11:0 for things other than addresses.
@@ -98,10 +106,18 @@ static void guest_test_unsupported_msr(const struct kvm_msr *msr)
 	u64 val;
 	u8 vec;
 
+	/*
+	 * Skip the RDMSR #GP test if the secondary feature is supported, as
+	 * only the to-be-written value depends on the primary feature.
+	 */
+	if (this_cpu_has(msr->feature2))
+		goto skip_rdmsr_gp;
+
 	vec = rdmsr_safe(msr->index, &val);
 	__GUEST_ASSERT(vec == GP_VECTOR, "Wanted #GP on RDMSR(0x%x), got %s",
 		       msr->index, ex_str(vec));
 
+skip_rdmsr_gp:
 	vec = wrmsr_safe(msr->index, msr->write_val);
 	__GUEST_ASSERT(vec == GP_VECTOR, "Wanted #GP on WRMSR(0x%x, 0x%lx), got %s",
 		       msr->index, msr->write_val, ex_str(vec));
@@ -224,6 +240,10 @@ static void test_msrs(void)
 		MSR_TEST_CANONICAL(MSR_CSTAR, LM),
 		MSR_TEST(MSR_SYSCALL_MASK, 0xffffffff, 0, LM),
 
+		MSR_TEST2(MSR_IA32_S_CET, CET_SHSTK_EN, CET_RESERVED, SHSTK, IBT),
+		MSR_TEST2(MSR_IA32_S_CET, CET_ENDBR_EN, CET_RESERVED, IBT, SHSTK),
+		MSR_TEST2(MSR_IA32_U_CET, CET_SHSTK_EN, CET_RESERVED, SHSTK, IBT),
+		MSR_TEST2(MSR_IA32_U_CET, CET_ENDBR_EN, CET_RESERVED, IBT, SHSTK),
 		MSR_TEST_CANONICAL(MSR_IA32_PL0_SSP, SHSTK),
 		MSR_TEST(MSR_IA32_PL0_SSP, canonical_val, canonical_val | 1, SHSTK),
 		MSR_TEST_CANONICAL(MSR_IA32_PL1_SSP, SHSTK),
-- 
2.51.0.384.g4c02a37b29-goog