The LFENCE always serializing feature bit was defined as scattered
LFENCE_RDTSC and its native leaf bit position open-coded for KVM.
Add it to its newly added CPUID leaf 0x80000021 EAX proper.
With LFENCE_RDTSC is in its proper place, the kernel's set_cpu_cap()
will effectively sythesize the feature for KVM going forward.
Drop the bit description comments now it's more self-describing.
Also, in amd_init(), don't bother setting DE_CFG[1] any more.
Signed-off-by: Kim Phillips <kim.phillips@xxxxxxx>
---
arch/x86/include/asm/cpufeatures.h | 3 ++-
arch/x86/kernel/cpu/amd.c | 2 +-
arch/x86/kvm/cpuid.c | 5 +----
3 files changed, 4 insertions(+), 6 deletions(-)
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 4637fd7a84d6..e975822951b2 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -97,7 +97,7 @@
#define X86_FEATURE_SYSENTER32 ( 3*32+15) /* "" sysenter in IA32 userspace */
#define X86_FEATURE_REP_GOOD ( 3*32+16) /* REP microcode works well */
#define X86_FEATURE_AMD_LBR_V2 ( 3*32+17) /* AMD Last Branch Record Extension Version 2 */
-#define X86_FEATURE_LFENCE_RDTSC ( 3*32+18) /* "" LFENCE synchronizes RDTSC */
+/* FREE, was #define X86_FEATURE_LFENCE_RDTSC ( 3*32+18) "" LFENCE synchronizes RDTSC */
#define X86_FEATURE_ACC_POWER ( 3*32+19) /* AMD Accumulated Power Mechanism */
#define X86_FEATURE_NOPL ( 3*32+20) /* The NOPL (0F 1F) instructions */
#define X86_FEATURE_ALWAYS ( 3*32+21) /* "" Always-present feature */
@@ -432,6 +432,7 @@
/* AMD-defined Extended Feature 2 EAX, CPUID level 0x80000021 (EAX), word 20 */
#define X86_FEATURE_NO_NESTED_DATA_BP (20*32+ 0) /* "" No Nested Data Breakpoints */
+#define X86_FEATURE_LFENCE_RDTSC (20*32+ 2) /* "" LFENCE always serializing / synchronizes RDTSC */
/*
* BUG word(s)
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index f769d6d08b43..208c2ce8598a 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -956,7 +956,7 @@ static void init_amd(struct cpuinfo_x86 *c)
init_amd_cacheinfo(c);
- if (cpu_has(c, X86_FEATURE_XMM2)) {
+ if (!cpu_has(c, X86_FEATURE_LFENCE_RDTSC) && cpu_has(c, X86_FEATURE_XMM2)) {
/*
* Use LFENCE for execution serialization. On families which
* don't have that MSR, LFENCE is already serializing.
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 9764499acce2..448b5de98b8f 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -742,12 +742,9 @@ void kvm_set_cpu_caps(void)
F(SME_COHERENT));
kvm_cpu_cap_mask(CPUID_8000_0021_EAX,
- F(NO_NESTED_DATA_BP) |
- BIT(2) /* LFENCE Always serializing */ | 0 /* SmmPgCfgLock */ |
+ F(NO_NESTED_DATA_BP) | F(LFENCE_RDTSC) | 0 /* SmmPgCfgLock */ |
BIT(6) /* NULL_SEL_CLR_BASE */ | 0 /* PrefetchCtlMsr */
);
- if (cpu_feature_enabled(X86_FEATURE_LFENCE_RDTSC))
- kvm_cpu_caps[CPUID_8000_0021_EAX] |= BIT(2) /* LFENCE Always serializing */;
if (!static_cpu_has_bug(X86_BUG_NULL_SEG))
kvm_cpu_caps[CPUID_8000_0021_EAX] |= BIT(6) /* NULL_SEL_CLR_BASE */;
kvm_cpu_caps[CPUID_8000_0021_EAX] |= BIT(9) /* NO_SMM_CTL_MSR */;
--
2.34.1
