[for-4.18][PATCH 0/2] Fix AMD erratum #1485 on AMD Zen4

[Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>]

This patch should make it to 4.18, as it prevents random crashes on AMD
Zen4 running outdated microcode.

Under certain conditions Zen4 may corrupt its own code stream when SMT is
enabled and STIBP is not. The Linux thread in which this was highlighted is
in patch2's commit message.

NOTE: Still running in CI as of now, but tested locally. Pipeline here.
    https://gitlab.com/xen-project/people/agvallejo/xen/-/pipelines/1034895039

Patch 1: is just a minor refactor to ensure we don't get microarchitectures
         of different families mixed up now that we have 3 different
         families involved (Fam17h, Fam18h and Fam19h)
Patch 2: The actual fix. It involves setting a bit in an MSR if it's a non
         virtualized zen4. It's not a direct copy of the Linux patch, as we
         have started using macros to find out microarchitectures from
         CPUID bits, rather than relying on models.

Alejandro Vallejo (2):
  xen/x86: Add family guards to the is_zen[12]_uarch() macros
  x86/amd: Prevent potentially fetching wrong instruction bytes on Zen4

 xen/arch/x86/cpu/amd.c               | 16 +++++++++++++---
 xen/arch/x86/include/asm/amd.h       | 17 +++++++++++++----
 xen/arch/x86/include/asm/msr-index.h |  2 ++
 xen/arch/x86/spec_ctrl.c             |  3 ---
 4 files changed, 28 insertions(+), 10 deletions(-)

-- 
2.34.1