linux-kernel - Re: [PATCH 2/4] KVM: x86: Advertise AMX CPUIDs in subleaf 0x1E.0x1 to userspace

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <cf20fff4-931a-4a07-83c1-a33de13fa230@intel.com>
Date: Fri, 23 Jan 2026 14:02:42 +0800
From: Xiaoyao Li <xiaoyao.li@...el.com>
To: Zhao Liu <zhao1.liu@...el.com>, Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
 Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
 "H . Peter Anvin" <hpa@...or.com>, Paolo Bonzini <pbonzini@...hat.com>,
 Sean Christopherson <seanjc@...gle.com>, kvm@...r.kernel.org,
 linux-kernel@...r.kernel.org
Cc: Chao Gao <chao.gao@...el.com>, Xudong Hao <xudong.hao@...el.com>
Subject: Re: [PATCH 2/4] KVM: x86: Advertise AMX CPUIDs in subleaf 0x1E.0x1 to
 userspace

On 11/20/2025 1:07 PM, Zhao Liu wrote:
> In addition to the new features, CPUID 0x1E.0x1.EAX[bits 0-3] are
> mirrored positions of existing AMX feature bits distributed across the
> 0x7 leaves. To avoid duplicate feature names, name these mirror bits
> with a *_MIRROR suffix, and define them in reverse_cpuid.h as KVM-only
> features as well.

It looks that KVM can emulate the mirroring CPUIDs regardless of whether 
hardware supports subleaf 1. However, given such emulation provides no 
real benefit but complicates KVM implementation, this patch looks good 
to me.