linux-kernel - Re: [PATCH v7 03/10] x86/cpufeatures: Add the CPUID feature bit for NMI-source reporting

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Message-ID: <70b7f6ba-1f13-4af0-b27e-064d6aaa5334@zytor.com>
Date: Wed, 18 Jun 2025 22:06:20 -0700
From: Xin Li <xin@...or.com>
To: Sohil Mehta <sohil.mehta@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Cc: "H . Peter Anvin" <hpa@...or.com>, Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Kan Liang <kan.liang@...ux.intel.com>, Tony Luck <tony.luck@...el.com>,
        Zhang Rui <rui.zhang@...el.com>, Steven Rostedt <rostedt@...dmis.org>,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Jacob Pan <jacob.pan@...ux.microsoft.com>,
        Andi Kleen <ak@...ux.intel.com>, Kai Huang <kai.huang@...el.com>,
        Sandipan Das <sandipan.das@....com>, linux-perf-users@...r.kernel.org,
        linux-edac@...r.kernel.org, kvm@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH v7 03/10] x86/cpufeatures: Add the CPUID feature bit for
 NMI-source reporting

On 6/12/2025 2:48 PM, Sohil Mehta wrote:
> NMI-source reporting is introduced to report the sources of NMIs with
> FRED event delivery based on vectors in NMI interrupt messages or the
> local APIC. This enables the kernel to avoid the latency incurred by
> going over the entire NMI handler list and reduces ambiguity about the
> source of an NMI.
> 
> Enumerate NMI-source reporting in cpufeatures.h. Also, since NMI-source
> reporting uses the FRED event dispatch framework, make it dependent on
> FRED in the CPUID dependency table. This ensures that NMI-source
> reporting gets disabled when FRED is disabled.
> 
> NMI-source reporting is intended as a kernel feature and does not need
> userspace enumeration or configuration. There is no need to expose it to
> userspace through /proc/cpuinfo.
> 
> Originally-by: Jacob Pan<jacob.jun.pan@...ux.intel.com>
> Signed-off-by: Sohil Mehta<sohil.mehta@...el.com>

Reviewed-by: Xin Li (Intel) <xin@...or.com>