linux-kernel - Re: [PATCH] KVM: x86: Virtualize AMD CPUID faulting

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Message-ID: <CALMp9eRGVC-xtH1aVSVXwZZFskyWVNWzqcB2PHjM3qmbNK6m6w@mail.gmail.com>
Date: Tue, 10 Feb 2026 15:23:47 -0800
From: Jim Mattson <jmattson@...gle.com>
To: Jamie Liu <jamieliu@...gle.com>
Cc: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>, 
	Borislav Petkov <bp@...en8.de>, Thomas Gleixner <tglx@...nel.org>, Ingo Molnar <mingo@...hat.com>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	"H. Peter Anvin" <hpa@...or.com>, kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: x86: Virtualize AMD CPUID faulting

On Tue, Feb 10, 2026 at 1:09 PM Jamie Liu <jamieliu@...gle.com> wrote:
>
> CPUID faulting via MSR_MISC_FEATURES_ENABLES_CPUID_FAULT is only used on
> Intel CPUs. The mechanism virtualized by this change is used on AMD
> CPUs. See arch/x86/kernel/cpu/amd.c:bsp_init_amd(),
> arch/x86/kernel/process.c:set_cpuid_faulting().
>
> Signed-off-by: Jamie Liu <jamieliu@...gle.com>

You missed the cpuid faulting check in em_cpuid():

ctxt->ops->get_msr(ctxt, MSR_MISC_FEATURES_ENABLES, &msr);
if (msr & MSR_MISC_FEATURES_ENABLES_CPUID_FAULT &&
    ctxt->ops->cpl(ctxt)) {
return emulate_gp(ctxt, 0);
}