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| author | Ross Zwisler <ross.zwisler@linux.intel.com> | 2018-02-03 00:26:26 -0700 |
|---|---|---|
| committer | Ross Zwisler <ross.zwisler@linux.intel.com> | 2018-02-03 00:26:26 -0700 |
| commit | ee95f4059a833839bf52972191b2d4c3d3cec552 (patch) | |
| tree | a1c8587d9b82e64a75dde376a90a3d69b0f4847a /arch/x86/kernel/cpu/amd.c | |
| parent | d121f07691415df824e6b60520f782f6d13b3c81 (diff) | |
| parent | f81e1d35a6e36d30888c46283b8dd1022e847124 (diff) | |
| download | op-kernel-dev-ee95f4059a833839bf52972191b2d4c3d3cec552.zip op-kernel-dev-ee95f4059a833839bf52972191b2d4c3d3cec552.tar.gz | |
Merge branch 'for-4.16/nfit' into libnvdimm-for-next
Diffstat (limited to 'arch/x86/kernel/cpu/amd.c')
| -rw-r--r-- | arch/x86/kernel/cpu/amd.c | 28 |
1 files changed, 26 insertions, 2 deletions
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index bcb75dc..ea831c8 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -829,8 +829,32 @@ static void init_amd(struct cpuinfo_x86 *c) set_cpu_cap(c, X86_FEATURE_K8); if (cpu_has(c, X86_FEATURE_XMM2)) { - /* MFENCE stops RDTSC speculation */ - set_cpu_cap(c, X86_FEATURE_MFENCE_RDTSC); + unsigned long long val; + int ret; + + /* + * A serializing LFENCE has less overhead than MFENCE, so + * use it 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. + */ + 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); + } } /* |
