linux-kernel - RE: [PATCH v7 05/10] x86/nmi: Assign and register NMI-source vectors

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Message-ID: <CY8PR11MB71344115BD680973922C3670894EA@CY8PR11MB7134.namprd11.prod.outlook.com>
Date: Tue, 8 Jul 2025 07:30:52 +0000
From: "Zhuo, Qiuxu" <qiuxu.zhuo@...el.com>
To: "Mehta, Sohil" <sohil.mehta@...el.com>, "x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC: Xin Li <xin@...or.com>, "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>, "Hunter, Adrian"
	<adrian.hunter@...el.com>, Kan Liang <kan.liang@...ux.intel.com>, "Luck,
 Tony" <tony.luck@...el.com>, "Zhang, Rui" <rui.zhang@...el.com>, "Steven
 Rostedt" <rostedt@...dmis.org>, "andrew.cooper3@...rix.com"
	<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>, "Huang, Kai" <kai.huang@...el.com>, Sandipan
 Das <sandipan.das@....com>, "linux-perf-users@...r.kernel.org"
	<linux-perf-users@...r.kernel.org>, "linux-edac@...r.kernel.org"
	<linux-edac@...r.kernel.org>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-trace-kernel@...r.kernel.org" <linux-trace-kernel@...r.kernel.org>
Subject: RE: [PATCH v7 05/10] x86/nmi: Assign and register NMI-source vectors

> From: Mehta, Sohil <sohil.mehta@...el.com>
> [...]
> >> Platform NMI handlers have a single handler registered per type. They
> >> don't
> >
> > From the current NMI code point of view [1] or [2], a type of platform
> > NMI handler may have multiple handlers registered.
> >
> > [1]
> > https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> > /tree/arch/x86/kernel/nmi.c#n199 [2]
> > https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> > /tree/arch/x86/kernel/nmi.c#n201
> >
> 
> We have warnings that should flag any time multiple handlers are registered
> for SERR or IO_CHK:
> 
> 	/*
> 	 * Indicate if there are multiple registrations on the
> 	 * internal NMI handler call chains (SERR and IO_CHECK).
> 	 */
> 	WARN_ON_ONCE(type == NMI_SERR && !list_empty(&desc->head));
> 	WARN_ON_ONCE(type == NMI_IO_CHECK && !list_empty(&desc-
> >head));
> 

The warning doesn't imply that it must be a single NMI handler. 
Otherwise, why not use a single NMI callback pointer per platform NMI 
type for registration in the current NMI code? 

I just don't want your comments or commit messages to 
mismatch the current code as it stands.

-Qiuxu