[PATCH v10 26/28] KVM: selftests: Add FRED MSRs to msrs_test
From: Sohil Mehta
Date: Fri Sep 11 2026 - 17:59:17 EST
From: Xin Li <xin@xxxxxxxxx>
Add FRED MSR coverage to msrs_test, including the FRED RSP0-3, SSP0-3,
STKLVLS and CONFIG MSRs.
Signed-off-by: Xin Li <xin@xxxxxxxxx>
Signed-off-by: Sohil Mehta <sohil.mehta@xxxxxxxxx>
---
v10:
- New patch.
---
tools/arch/x86/include/asm/msr-index.h | 2 +
.../selftests/kvm/include/x86/processor.h | 1 +
tools/testing/selftests/kvm/x86/msrs_test.c | 52 ++++++++++++++++++-
3 files changed, 53 insertions(+), 2 deletions(-)
diff --git a/tools/arch/x86/include/asm/msr-index.h b/tools/arch/x86/include/asm/msr-index.h
index 18c4be75e927..14632e29f981 100644
--- a/tools/arch/x86/include/asm/msr-index.h
+++ b/tools/arch/x86/include/asm/msr-index.h
@@ -64,6 +64,8 @@
#define MSR_IA32_FRED_SSP3 0x1d3 /* Level 3 shadow stack pointer */
#define MSR_IA32_FRED_CONFIG 0x1d4 /* Entrypoint and interrupt stack level */
+#define FRED_CONFIG_RESERVED (BIT_ULL(2) | GENMASK_ULL(5, 4) | BIT_ULL(11))
+
/* Intel MSRs. Some also available on other CPUs */
#define MSR_TEST_CTRL 0x00000033
#define MSR_TEST_CTRL_SPLIT_LOCK_DETECT_BIT 29
diff --git a/tools/testing/selftests/kvm/include/x86/processor.h b/tools/testing/selftests/kvm/include/x86/processor.h
index 6e6f70035508..916646cb4d89 100644
--- a/tools/testing/selftests/kvm/include/x86/processor.h
+++ b/tools/testing/selftests/kvm/include/x86/processor.h
@@ -195,6 +195,7 @@ struct kvm_x86_cpu_feature {
#define X86_FEATURE_SPEC_CTRL KVM_X86_CPU_FEATURE(0x7, 0, EDX, 26)
#define X86_FEATURE_ARCH_CAPABILITIES KVM_X86_CPU_FEATURE(0x7, 0, EDX, 29)
#define X86_FEATURE_PKS KVM_X86_CPU_FEATURE(0x7, 0, ECX, 31)
+#define X86_FEATURE_FRED KVM_X86_CPU_FEATURE(0x7, 1, EAX, 17)
#define X86_FEATURE_XTILECFG KVM_X86_CPU_FEATURE(0xD, 0, EAX, 17)
#define X86_FEATURE_XTILEDATA KVM_X86_CPU_FEATURE(0xD, 0, EAX, 18)
#define X86_FEATURE_XSAVES KVM_X86_CPU_FEATURE(0xD, 1, EAX, 3)
diff --git a/tools/testing/selftests/kvm/x86/msrs_test.c b/tools/testing/selftests/kvm/x86/msrs_test.c
index f7e39bf887ad..6e2d8b8f1bd3 100644
--- a/tools/testing/selftests/kvm/x86/msrs_test.c
+++ b/tools/testing/selftests/kvm/x86/msrs_test.c
@@ -60,9 +60,23 @@ static const u64 u64_val = 0xaaaa5555aaaa5555ull;
#define MSR_TEST_CANONICAL(msr, feat) \
__MSR_TEST(msr, #msr, canonical_val, NONCANONICAL, 0, feat)
+#define MSR_TEST_CANONICAL2(msr, feat, f2) \
+ ____MSR_TEST(msr, #msr, canonical_val, NONCANONICAL, 0, feat, f2, false)
+
#define MSR_TEST_KVM(msr, val, rsvd, feat) \
____MSR_TEST(KVM_REG_ ##msr, #msr, val, rsvd, 0, feat, feat, true)
+/* FRED RSPs are 64-byte aligned, thus bits 5:0 are all zero */
+static const u64 fred_rsp_canonical_val = canonical_val + 0xbc0;
+
+/*
+ * FRED SSP[123] are 8-byte aligned, thus bits 2:0 are all zero.
+ *
+ * For legacy reasons, FRED SSP0 is allowed to be 4-byte aligned, but treat
+ * it as 8-byte aligned to simplify the tests.
+ */
+static const u64 fred_ssp_canonical_val = canonical_val + 0xbc8;
+
/*
* The main struct must be scoped to a function due to the use of structures to
* define features. For the global structure, allocate enough space for the
@@ -388,8 +402,9 @@ static void test_msrs(void)
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_CANONICAL2(MSR_IA32_PL0_SSP, SHSTK, FRED),
+ MSR_TEST2(MSR_IA32_PL0_SSP, canonical_val, canonical_val | 1, SHSTK, FRED),
+ MSR_TEST2(MSR_IA32_PL0_SSP, canonical_val, canonical_val | 1, FRED, SHSTK),
MSR_TEST_CANONICAL(MSR_IA32_PL1_SSP, SHSTK),
MSR_TEST(MSR_IA32_PL1_SSP, canonical_val, canonical_val | 1, SHSTK),
MSR_TEST_CANONICAL(MSR_IA32_PL2_SSP, SHSTK),
@@ -398,10 +413,35 @@ static void test_msrs(void)
MSR_TEST(MSR_IA32_PL3_SSP, canonical_val, canonical_val | 1, SHSTK),
MSR_TEST_KVM(GUEST_SSP, canonical_val, NONCANONICAL, SHSTK),
+
+ MSR_TEST_CANONICAL(MSR_IA32_FRED_RSP0, FRED),
+ MSR_TEST(MSR_IA32_FRED_RSP0, fred_rsp_canonical_val, fred_rsp_canonical_val | 1, FRED),
+ MSR_TEST_CANONICAL(MSR_IA32_FRED_RSP1, FRED),
+ MSR_TEST(MSR_IA32_FRED_RSP1, fred_rsp_canonical_val, fred_rsp_canonical_val | 2, FRED),
+ MSR_TEST_CANONICAL(MSR_IA32_FRED_RSP2, FRED),
+ MSR_TEST(MSR_IA32_FRED_RSP2, fred_rsp_canonical_val, fred_rsp_canonical_val | 4, FRED),
+ MSR_TEST_CANONICAL(MSR_IA32_FRED_RSP3, FRED),
+ MSR_TEST(MSR_IA32_FRED_RSP3, fred_rsp_canonical_val, fred_rsp_canonical_val | 7, FRED),
+
+ MSR_TEST_CANONICAL2(MSR_IA32_FRED_SSP0, FRED, SHSTK),
+ MSR_TEST2(MSR_IA32_FRED_SSP0, fred_ssp_canonical_val, fred_ssp_canonical_val | 1, SHSTK, FRED),
+ MSR_TEST2(MSR_IA32_FRED_SSP0, fred_ssp_canonical_val, fred_ssp_canonical_val | 1, FRED, SHSTK),
+ MSR_TEST_CANONICAL(MSR_IA32_FRED_SSP1, FRED),
+ MSR_TEST(MSR_IA32_FRED_SSP1, fred_ssp_canonical_val, fred_ssp_canonical_val | 2, FRED),
+ MSR_TEST_CANONICAL(MSR_IA32_FRED_SSP2, FRED),
+ MSR_TEST(MSR_IA32_FRED_SSP2, fred_ssp_canonical_val, fred_ssp_canonical_val | 4, FRED),
+ MSR_TEST_CANONICAL(MSR_IA32_FRED_SSP3, FRED),
+ MSR_TEST(MSR_IA32_FRED_SSP3, fred_ssp_canonical_val, fred_ssp_canonical_val | 7, FRED),
+
+ MSR_TEST(MSR_IA32_FRED_STKLVLS, 0xe41be41be41be41b, 0, FRED),
+
+ MSR_TEST_CANONICAL(MSR_IA32_FRED_CONFIG, FRED),
+ MSR_TEST(MSR_IA32_FRED_CONFIG, canonical_val, canonical_val | FRED_CONFIG_RESERVED, FRED),
};
const struct kvm_x86_cpu_feature feat_none = X86_FEATURE_NONE;
const struct kvm_x86_cpu_feature feat_lm = X86_FEATURE_LM;
+ const struct kvm_x86_cpu_feature feat_fred = X86_FEATURE_FRED;
/*
* Create three vCPUs, but run them on the same task, to validate KVM's
@@ -432,6 +472,14 @@ static void test_msrs(void)
* immutable once the vCPU has been run.
*/
for (idx = 0; idx < ARRAY_SIZE(__msrs); idx++) {
+ /*
+ * Feature word 0x7:1:EAX used by FRED doesn't exist on some CPU
+ * models, simply skip clearing FRED feature bit.
+ */
+ if (!memcmp(&msrs[idx].feature, &feat_fred, sizeof(feat_fred)) &&
+ !kvm_cpu_has(X86_FEATURE_FRED))
+ continue;
+
/*
* Don't clear LM; selftests are 64-bit only, and KVM doesn't
* honor LM=0 for MSRs that are supposed to exist if and only
--
2.43.0