diff options
Diffstat (limited to 'arch/x86/include/asm/msr.h')
| -rw-r--r-- | arch/x86/include/asm/msr.h | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h index 91e4cf189914..5cc3930cb465 100644 --- a/arch/x86/include/asm/msr.h +++ b/arch/x86/include/asm/msr.h @@ -217,6 +217,8 @@ static __always_inline unsigned long long rdtsc(void) */ static __always_inline unsigned long long rdtsc_ordered(void) { + DECLARE_ARGS(val, low, high); + /* * The RDTSC instruction is not ordered relative to memory * access. The Intel SDM and the AMD APM are both vague on this @@ -227,9 +229,19 @@ static __always_inline unsigned long long rdtsc_ordered(void) * ordering guarantees as reading from a global memory location * that some other imaginary CPU is updating continuously with a * time stamp. + * + * Thus, use the preferred barrier on the respective CPU, aiming for + * RDTSCP as the default. */ - barrier_nospec(); - return rdtsc(); + asm volatile(ALTERNATIVE_3("rdtsc", + "mfence; rdtsc", X86_FEATURE_MFENCE_RDTSC, + "lfence; rdtsc", X86_FEATURE_LFENCE_RDTSC, + "rdtscp", X86_FEATURE_RDTSCP) + : EAX_EDX_RET(val, low, high) + /* RDTSCP clobbers ECX with MSR_TSC_AUX. */ + :: "ecx"); + + return EAX_EDX_VAL(val, low, high); } static inline unsigned long long native_read_pmc(int counter) |