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-rw-r--r--arch/x86/include/asm/barrier.h3
-rw-r--r--arch/x86/include/asm/cpufeatures.h1
-rw-r--r--arch/x86/include/asm/msr.h3
-rw-r--r--arch/x86/kernel/cpu/amd.c21
-rw-r--r--arch/x86/kernel/cpu/hygon.c21
-rw-r--r--tools/arch/x86/include/asm/cpufeatures.h1
6 files changed, 8 insertions, 42 deletions
diff --git a/arch/x86/include/asm/barrier.h b/arch/x86/include/asm/barrier.h
index 84f848c2541a..7f828fe49797 100644
--- a/arch/x86/include/asm/barrier.h
+++ b/arch/x86/include/asm/barrier.h
@@ -49,8 +49,7 @@ static inline unsigned long array_index_mask_nospec(unsigned long index,
#define array_index_mask_nospec array_index_mask_nospec
/* Prevent speculative execution past this barrier. */
-#define barrier_nospec() alternative_2("", "mfence", X86_FEATURE_MFENCE_RDTSC, \
- "lfence", X86_FEATURE_LFENCE_RDTSC)
+#define barrier_nospec() alternative("", "lfence", X86_FEATURE_LFENCE_RDTSC)
#define dma_rmb() barrier()
#define dma_wmb() barrier()
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 56f53bf3bbbf..fcc70ffd88c2 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -96,7 +96,6 @@
#define X86_FEATURE_SYSCALL32 ( 3*32+14) /* "" syscall in IA32 userspace */
#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_MFENCE_RDTSC ( 3*32+17) /* "" MFENCE synchronizes RDTSC */
#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 */
diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 5cc3930cb465..86f20d520a07 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -233,8 +233,7 @@ static __always_inline unsigned long long rdtsc_ordered(void)
* Thus, use the preferred barrier on the respective CPU, aiming for
* RDTSCP as the default.
*/
- asm volatile(ALTERNATIVE_3("rdtsc",
- "mfence; rdtsc", X86_FEATURE_MFENCE_RDTSC,
+ asm volatile(ALTERNATIVE_2("rdtsc",
"lfence; rdtsc", X86_FEATURE_LFENCE_RDTSC,
"rdtscp", X86_FEATURE_RDTSCP)
: EAX_EDX_RET(val, low, high)
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 8d4e50428b68..3afe07d602dd 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -879,12 +879,8 @@ static void init_amd(struct cpuinfo_x86 *c)
init_amd_cacheinfo(c);
if (cpu_has(c, X86_FEATURE_XMM2)) {
- unsigned long long val;
- int ret;
-
/*
- * A serializing LFENCE has less overhead than MFENCE, so
- * use it for execution serialization. On families which
+ * Use LFENCE for execution serialization. On families which
* don't have that MSR, LFENCE is already serializing.
* msr_set_bit() uses the safe accessors, too, even if the MSR
* is not present.
@@ -892,19 +888,8 @@ static void init_amd(struct cpuinfo_x86 *c)
msr_set_bit(MSR_F10H_DECFG,
MSR_F10H_DECFG_LFENCE_SERIALIZE_BIT);
- /*
- * Verify that the MSR write was successful (could be running
- * under a hypervisor) and only then assume that LFENCE is
- * serializing.
- */
- ret = rdmsrl_safe(MSR_F10H_DECFG, &val);
- if (!ret && (val & MSR_F10H_DECFG_LFENCE_SERIALIZE)) {
- /* A serializing LFENCE stops RDTSC speculation */
- set_cpu_cap(c, X86_FEATURE_LFENCE_RDTSC);
- } else {
- /* MFENCE stops RDTSC speculation */
- set_cpu_cap(c, X86_FEATURE_MFENCE_RDTSC);
- }
+ /* A serializing LFENCE stops RDTSC speculation */
+ set_cpu_cap(c, X86_FEATURE_LFENCE_RDTSC);
}
/*
diff --git a/arch/x86/kernel/cpu/hygon.c b/arch/x86/kernel/cpu/hygon.c
index 415621ddb8a2..4e28c1fc8749 100644
--- a/arch/x86/kernel/cpu/hygon.c
+++ b/arch/x86/kernel/cpu/hygon.c
@@ -330,12 +330,8 @@ static void init_hygon(struct cpuinfo_x86 *c)
init_hygon_cacheinfo(c);
if (cpu_has(c, X86_FEATURE_XMM2)) {
- unsigned long long val;
- int ret;
-
/*
- * A serializing LFENCE has less overhead than MFENCE, so
- * use it for execution serialization. On families which
+ * Use LFENCE for execution serialization. On families which
* don't have that MSR, LFENCE is already serializing.
* msr_set_bit() uses the safe accessors, too, even if the MSR
* is not present.
@@ -343,19 +339,8 @@ static void init_hygon(struct cpuinfo_x86 *c)
msr_set_bit(MSR_F10H_DECFG,
MSR_F10H_DECFG_LFENCE_SERIALIZE_BIT);
- /*
- * Verify that the MSR write was successful (could be running
- * under a hypervisor) and only then assume that LFENCE is
- * serializing.
- */
- ret = rdmsrl_safe(MSR_F10H_DECFG, &val);
- if (!ret && (val & MSR_F10H_DECFG_LFENCE_SERIALIZE)) {
- /* A serializing LFENCE stops RDTSC speculation */
- set_cpu_cap(c, X86_FEATURE_LFENCE_RDTSC);
- } else {
- /* MFENCE stops RDTSC speculation */
- set_cpu_cap(c, X86_FEATURE_MFENCE_RDTSC);
- }
+ /* A serializing LFENCE stops RDTSC speculation */
+ set_cpu_cap(c, X86_FEATURE_LFENCE_RDTSC);
}
/*
diff --git a/tools/arch/x86/include/asm/cpufeatures.h b/tools/arch/x86/include/asm/cpufeatures.h
index 998c2cc08363..9b98edb6b2d3 100644
--- a/tools/arch/x86/include/asm/cpufeatures.h
+++ b/tools/arch/x86/include/asm/cpufeatures.h
@@ -96,7 +96,6 @@
#define X86_FEATURE_SYSCALL32 ( 3*32+14) /* "" syscall in IA32 userspace */
#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_MFENCE_RDTSC ( 3*32+17) /* "" MFENCE synchronizes RDTSC */
#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 */