linux-kernel - Re: [PATCH 5/9] x86/nmi: Fix comment in unknown NMI handling

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Message-ID: <BF35DF73-974C-4C8F-8ECE-3C9C254BAD1C@zytor.com>
Date: Mon, 31 Mar 2025 22:45:41 -0700
From: "H. Peter Anvin" <hpa@...or.com>
To: "Huang, Kai" <kai.huang@...el.com>, "Mehta, Sohil" <sohil.mehta@...el.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "x86@...nel.org" <x86@...nel.org>
CC: "Nikula, Jani" <jani.nikula@...el.com>, "bp@...en8.de" <bp@...en8.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "rppt@...nel.org" <rppt@...nel.org>,
        "bigeasy@...utronix.de" <bigeasy@...utronix.de>,
        "jpoimboe@...nel.org" <jpoimboe@...nel.org>,
        "pmladek@...e.com" <pmladek@...e.com>, "xin@...or.com" <xin@...or.com>,
        "Luck, Tony" <tony.luck@...el.com>
Subject: Re: [PATCH 5/9] x86/nmi: Fix comment in unknown NMI handling

On March 31, 2025 5:17:55 PM PDT, "Huang, Kai" <kai.huang@...el.com> wrote:
>On Thu, 2025-03-27 at 23:46 +0000, Mehta, Sohil wrote:
>> The comment in unknown NMI handling is incorrect and misleading. There
>> is no longer a restriction on having a single Unknown NMI handler. Also,
>> nmi_handle() does not use the 'b2b' parameter anymore.
>> 
>> The changes that made the comment outdated are:
>> 
>> commit 0d443b70cc92 ("x86/platform: Remove warning message for duplicate
>> NMI handlers")
>> 
>> commit bf9f2ee28d47 ("x86/nmi: Remove the 'b2b' parameter from
>> nmi_handle()")
>
>After some digging, IIUC, the 'b2b' parameter of the nmi_handle() was actually
>never used when it was originally added in the 
>
>  commit b227e23399dc ("x86, nmi: Add in logic to handle multiple events and
>unknown NMIs")
>
>.., so IIUC the comment was wrong when it was firstly added.  
>
>The above commit to remove the 'b2b' seems just a fixup patch but it didn't fix
>the comment.
>
>Not sure whether it is worth to mention in the changelog.
>
>> 
>> Remove the old comment and update it to reflect the current intention.
>> 
>> Signed-off-by: Sohil Mehta <sohil.mehta@...el.com>
>> 
>
>Anyway:
>
>Reviewed-by: Kai Huang <kai.huang@...el.com>
>

Ha! Any idea what it was *supposed* to do? I'm guessing it stood for "back to back" or some such?