git: nvmm: Ignore MSR_LS_CFG (0xC0011020) on AMD CPUs

[Aaron LI]

commit 1085a76fa5fecc6be80c38c25edf2b75780b1b21
Author: Aaron LI <aly at aaronly.me>
Date:   Fri Oct 2 21:37:36 2026 +0800

    nvmm: Ignore MSR_LS_CFG (0xC0011020) on AMD CPUs
    
    On older AMD CPUs that do not support SSBD mitigations, Linux falls
    back to writing to MSR_LS_CFG on each context switch if this MSR
    exists. This creates significant noise in the QEMU output.
    
    We can't simply inject #GP for accesses to this MSR, as that may
    break compatibility with older guests which assume that MSR_LS_CFG
    is present based solely on the reported CPU family and model.
    
    So just ignore this MSR completely. This fixes a QEMU output storm
    on Arch Linux (tested with archlinux-2019.05.02-x86_64.iso).
    
    Obtained-from: NVMM Reference Implementation

Summary of changes:
 sys/dev/virtual/nvmm/x86/nvmm_x86_internal.h | 1 +
 sys/dev/virtual/nvmm/x86/nvmm_x86_svm.c      | 6 ++++--
 2 files changed, 5 insertions(+), 2 deletions(-)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/1085a76fa5fecc6be80c38c25edf2b75780b1b21


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