git: DragonFly_RELEASE_6_4 nvmm(4): Expose ARCH_CAP to guest only if the host CPU supports it

[Aaron LI]

commit 2779004480b7c397519c2eee6647564271cdbfdf
Author: Aaron LI <aly at aaronly.me>
Date:   Mon Jan 26 14:23:29 2026 +0800

    nvmm(4): Expose ARCH_CAP to guest only if the host CPU supports it
    
    * Don't expose ARCH_CAP to guest on AMD CPUs, because the ARCH_CAP
      feature bit and the IA32_ARCH_CAPABILITIES MSR are Intel-specific and
      unavailable on AMD systems.  I decided to not follow Linux KVM, which
      chose to always provide ARCH_CAP and emulate the MSR for AMD CPUs.
    
    * Check whether the host CPU supports the ARCH_CAP feature bit and only
      expose it to the guest if the host supports it.
    
    Credit to tuxillo and Claude Opus LLM for the analyses and initial
    patches.

Summary of changes:
 sys/dev/virtual/nvmm/x86/nvmm_x86.c     |  4 ++--
 sys/dev/virtual/nvmm/x86/nvmm_x86_vmx.c | 21 ++++++++++++++-------
 2 files changed, 16 insertions(+), 9 deletions(-)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/2779004480b7c397519c2eee6647564271cdbfdf


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