[v1,0/3] target/i386: Add the immediate form MSR access instruction support

Message

Xin Li (Intel) Jan. 3, 2025, 8:48 a.m. UTC

The immediate form of MSR access instructions are primarily motivated by
performance, not code size: by having the MSR number in an immediate, it
is available *much* earlier in the pipeline, which allows the hardware
much more leeway about how a particular MSR is handled.

This new CPU feature is advertised through bit 5 of CPUID.7.1.ECX, which
needs to be added as a new CPU feature word.

WRMSRNS doesn't become a required feature for FERD, and Linux has removed
the dependency, as such remove the dependency from Qemu.


Xin Li (Intel) (3):
  target/i386: Remove FRED dependency on WRMSRNS
  target/i386: Add a new CPU feature word for CPUID.7.1.ECX
  target/i386: Add the immediate form MSR access instruction support

 target/i386/cpu.c | 27 ++++++++++++++++++++++-----
 target/i386/cpu.h |  4 ++++
 2 files changed, 26 insertions(+), 5 deletions(-)


base-commit: 1ada452efc7d8f8bf42cd5e8a2af1b4ac9167a1f