diff options
| author | David S. Miller <davem@davemloft.net> | 2018-01-17 00:00:25 -0500 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-01-17 00:10:42 -0500 |
| commit | c02b3741eb99a1ec733e6134c53ba59e43e19e97 (patch) | |
| tree | ff7dd96c32dec2abe530e7101378443dabcb8962 /arch/x86/kernel/cpu/amd.c | |
| parent | 7018d1b3f20fb4308ed9bc577160cb8ffb79b62a (diff) | |
| parent | 8cbab92dff778e516064c13113ca15d4869ec883 (diff) | |
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
Overlapping changes all over.
The mini-qdisc bits were a little bit tricky, however.
Signed-off-by: David S. Miller <davem@davemloft.net>
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 bcb75dc97d44..ea831c858195 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); + } } /* |