[PATCH v7 5/7] x86/cpu, kvm: Add the SMM_CTL MSR not present feature

Kim Phillips
2023-01-16T23:04:27Z

The SMM_CTL MSR not present feature was being open-coded for KVM in
__do_cpuid_func(). Add it to its newly added CPUID leaf 0x80000021 EAX
proper, and propagate it in kvm_set_cpu_caps() instead.

Also drop the bit description comments now the code is more
self-describing, and retain the SmmPgCfgLock and PrefetchCtlMsr feature
bit comments at the kvm_cpu_cap_mask() callsite.

Signed-off-by: Kim Phillips <kim.phillips@amd.com>
---
arch/x86/include/asm/cpufeatures.h | 1 +
arch/x86/kvm/cpuid.c | 13 +++----------
2 files changed, 4 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index ccef41ff718c..861d312c7955 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -432,6 +432,7 @@
#define X86_FEATURE_NO_NESTED_DATA_BP (20*32+ 0) /* "" AMD No Nested Data Breakpoints */
#define X86_FEATURE_LFENCE_RDTSC (20*32+ 2) /* "" LFENCE always serializing / synchronizes RDTSC */
#define X86_FEATURE_NULL_SEL_CLR_BASE (20*32+ 6) /* "" AMD Null Selector Clears Base */
+#define X86_FEATURE_NO_SMM_CTL_MSR (20*32+ 9) /* "" AMD SMM_CTL MSR is not present */

/*
* BUG word(s)
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index afa86241f752..9ba75ad9d976 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -742,12 +742,14 @@ void kvm_set_cpu_caps(void)
F(SME_COHERENT));

kvm_cpu_cap_mask(CPUID_8000_0021_EAX,
- F(NO_NESTED_DATA_BP) | F(LFENCE_RDTSC) | F(NULL_SEL_CLR_BASE)
+ F(NO_NESTED_DATA_BP) | F(LFENCE_RDTSC) | 0 /* SmmPgCfgLock */ |
+ F(NULL_SEL_CLR_BASE) | 0 /* PrefetchCtlMsr */
);
if (cpu_feature_enabled(X86_FEATURE_LFENCE_RDTSC))
kvm_cpu_cap_set(X86_FEATURE_LFENCE_RDTSC);
if (!static_cpu_has_bug(X86_BUG_NULL_SEG))
kvm_cpu_cap_set(X86_FEATURE_NULL_SEL_CLR_BASE);
+ kvm_cpu_cap_set(X86_FEATURE_NO_SMM_CTL_MSR);

kvm_cpu_cap_mask(CPUID_C000_0001_EDX,
F(XSTORE) | F(XSTORE_EN) | F(XCRYPT) | F(XCRYPT_EN) |
@@ -1231,15 +1233,6 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
case 0x80000021:
entry->ebx = entry->ecx = entry->edx = 0;
cpuid_entry_override(entry, CPUID_8000_0021_EAX);
- /*
- * Other defined bits are for MSRs that KVM does not expose:
- * EAX 3 SPCL, SMM page configuration lock
- * EAX 13 PCMSR, Prefetch control MSR
- *
- * KVM doesn't support SMM_CTL.
- * EAX 9 SMM_CTL MSR is not supported
- */
- entry->eax |= BIT(9);
break;
/*Add support for Centaur's CPUID instruction*/
case 0xC0000000:
--
2.34.1