[PATCH 0/4] x86/cpu: Use SERIALIZE in sync_core()

[Ricardo Neri]

A recent submission to LKML introduced a CPU feature flag for a new
Intel architecture Serializing Instruction, SERIALIZE [1]. Unlike the
existing Serializing Instructions, this new instruction does not have
side effects such as clobbering registers or exiting to a hypervisor.

As stated in the Intel "extensions" (ISE) manual [2], this instruction
will appear first in Sapphire Rapids and Alder Lake.

Andy Lutomirski suggested to use this instruction in sync_core() as it
serves the very purpose of this function [3].

For completeness, I picked patch #3 from Cathy's series (and has become
patch #1 here) [1]. Her series depends on such patch to build correctly.
Maybe it can be merged independently while the discussion continues?

Thanks and BR,
Ricardo

[1]. https://lore.kernel.org/kvm/1594088183-7187-1-git-send-email-cathy.zhang@xxxxxxxxx/
[2]. https://software.intel.com/sites/default/files/managed/c5/15/architecture-instruction-set-extensions-programming-reference.pdf
[3]. https://lore.kernel.org/kvm/CALCETrWudiF8G8r57r5i4JefuP5biG1kHg==0O8YXb-bYS-0BA@xxxxxxxxxxxxxx/

Ricardo Neri (4):
  x86/cpufeatures: Add enumeration for SERIALIZE instruction
  x86/cpu: Relocate sync_core() to sync_core.h
  x86/cpu: Refactor sync_core() for readability
  x86/cpu: Use SERIALIZE in sync_core() when available

 arch/x86/include/asm/cpufeatures.h   |  1 +
 arch/x86/include/asm/processor.h     | 64 ----------------------
 arch/x86/include/asm/special_insns.h |  4 ++
 arch/x86/include/asm/sync_core.h     | 80 ++++++++++++++++++++++++++++
 arch/x86/kernel/alternative.c        |  1 +
 arch/x86/kernel/cpu/mce/core.c       |  1 +
 drivers/misc/sgi-gru/grufault.c      |  1 +
 drivers/misc/sgi-gru/gruhandles.c    |  1 +
 drivers/misc/sgi-gru/grukservices.c  |  1 +
 9 files changed, 90 insertions(+), 64 deletions(-)

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2.17.1