From: Sean Christopherson <seanjc@google.com>
Date: Fri, 19 Sep 2025 22:32:53 +0000 (-0700)
Subject: KVM: selftests: Add support for MSR_IA32_{S,U}_CET to MSRs test
X-Git-Tag: v6.18-rc1~55^2~5^2~5
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=27c41353064f9fdec9276e6b8e618b01110ef282;p=thirdparty%2Flinux.git

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, but skip only RDMSR #GP tests to avoid false failures
when running on a CPU with only one of IBT or SHSTK (the WRMSR #GP tests
are still valid since the enable bits are per-feature).

Reviewed-by: Chao Gao <chao.gao@intel.com>
Link: https://lore.kernel.org/r/20250919223258.1604852-47-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
---

diff --git a/tools/testing/selftests/kvm/x86/msrs_test.c b/tools/testing/selftests/kvm/x86/msrs_test.c
index 345a39030a0a..1efaebb986c4 100644
--- a/tools/testing/selftests/kvm/x86/msrs_test.c
+++ b/tools/testing/selftests/kvm/x86/msrs_test.c
@@ -132,13 +132,26 @@ static void guest_test_unsupported_msr(const struct kvm_msr *msr)
 	if (ignore_unsupported_msrs)
 		goto skip_wrmsr_gp;
 
-	if (this_cpu_has(msr->feature2))
-		goto skip_wrmsr_gp;
+	/*
+	 * {S,U}_CET exist if IBT or SHSTK is supported, but with bits that are
+	 * writable only if their associated feature is supported.  Skip the
+	 * RDMSR #GP test if the secondary feature is supported, but perform
+	 * the WRMSR #GP test as the to-be-written value is tied to the primary
+	 * feature.  For all other MSRs, simply do nothing.
+	 */
+	if (this_cpu_has(msr->feature2)) {
+		if  (msr->index != MSR_IA32_U_CET &&
+		     msr->index != MSR_IA32_S_CET)
+			goto skip_wrmsr_gp;
+
+		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));
@@ -276,6 +289,10 @@ 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),