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

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Message-ID: <e01c2866-87d2-4881-9825-1b033dead5de@intel.com>
Date: Mon, 31 Mar 2025 22:53:04 -0700
From: Sohil Mehta <sohil.mehta@...el.com>
To: "H. Peter Anvin" <hpa@...or.com>, "Huang, Kai" <kai.huang@...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 3/31/2025 10:45 PM, H. Peter Anvin wrote:

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

Yes, it stands for back to back NMIs. I added additional comments to
clarify how they are detected.
https://lore.kernel.org/lkml/20250327234629.3953536-7-sohil.mehta@intel.com/

nmi_handle() still has special handling for back to back NMIs. But at
some point, there was a b2b parameter that was passed to nmi_handle().
AFAICT, that parameter was never really used.

Sohil