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author | Radim Krčmář <rkrcmar@redhat.com> | 2018-02-01 15:04:17 +0100 |
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committer | Radim Krčmář <rkrcmar@redhat.com> | 2018-02-01 15:04:17 +0100 |
commit | 7bf14c28ee776be567855bd39ed8ff795ea19f55 (patch) | |
tree | 6113748c673e85fccc2c56c050697789c00c6bc2 /arch/x86/kernel/cpu/amd.c | |
parent | 87cedc6be55954c6efd6eca2e694132513f65a2a (diff) | |
parent | 5fa4ec9cb2e6679e2f828033726f758ea314b9c5 (diff) | |
download | blackbird-obmc-linux-7bf14c28ee776be567855bd39ed8ff795ea19f55.tar.gz blackbird-obmc-linux-7bf14c28ee776be567855bd39ed8ff795ea19f55.zip |
Merge branch 'x86/hyperv' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Topic branch for stable KVM clockource under Hyper-V.
Thanks to Christoffer Dall for resolving the ARM conflict.
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 df8a2418aadf..5bddbdcbc4a3 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -855,8 +855,32 @@ 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); + } } /* |