To aid in speculation control, the LFENCE instruction will be turned into
a serializing instruction. There is less performance impact using LFENCE
in this way compared to MFENCE.
With LFENCE now being a serializing instruction, it can be used in
rdtsc_ordered() in place of MFENCE_RDTSC. The other two patches in this
series make this change and remove the MFENCE_RDTSC feature.
The following patches are included in this series:
- Make LFENCE a serializing instruction on AMD
- Change over to LFENCE_RDTSC from MFENCE_RDTSC on AMD
- Remove the MFENCE_RDTSC feature
This patch series is based on tip:x86/pti.
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Tom Lendacky (3):
x86/cpu/AMD: Make LFENCE a serializing instruction
x86/cpu/AMD: Use LFENCE_RDTSC instead of MFENCE_RDTSC
x86/msr: Remove now unused definition of MFENCE_RDTSC feature
arch/x86/include/asm/cpufeatures.h | 2 +-
arch/x86/include/asm/msr-index.h | 2 ++
arch/x86/include/asm/msr.h | 3 +--
arch/x86/kernel/cpu/amd.c | 13 +++++++++++--
4 files changed, 15 insertions(+), 5 deletions(-)
--
Tom Lendacky
