RFC x86/alternative: Add ALTERNATIVE_3

From: Borislav Petkov <[email protected]>

Hi,

here's a patchset which adds an ALTERNATIVE_3() macro so that we can finally do RDTSCP in rdtsc_ordered() but also not break all the possible qemu CPU models out there like some old pentium which doesn't have even MFENCE. Which is the reason for the three-insn alternative macro, btw.

The stuff works here on all machines I've tested it on but since we're too close to the merge window, I'll hold on to it for another round and let it soak slowly into 2019. Thus the RFC tag. In the meantime, it'll collect your comments and ideas.

:-)

Thanks!

Borislav Petkov (4):
x86/alternatives: Add macro comments
x86/alternatives: Print containing function
x86/alternatives: Add an ALTERNATIVE_3() macro
x86/TSC: Use RDTSCP

 arch/x86/include/asm/alternative.h | 39 ++++++++++++++++++++++++------
 arch/x86/include/asm/msr.h         | 16 ++++++++++--
 arch/x86/kernel/alternative.c      |  4 +--
 3 files changed, 48 insertions(+), 11 deletions(-)

2.19.1