linux-kernel - Re: [PATCH v2 2/6] x86/irq: Extend NMI handler registration interface to include source

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Message-ID: <20240627215630.5d7eba96@jacob-builder>
Date: Thu, 27 Jun 2024 21:56:30 -0700
From: Jacob Pan <jacob.jun.pan@...ux.intel.com>
To: Sohil Mehta <sohil.mehta@...el.com>
Cc: X86 Kernel <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>, Thomas
 Gleixner <tglx@...utronix.de>, Dave Hansen <dave.hansen@...el.com>, "H.
 Peter Anvin" <hpa@...or.com>, "Ingo Molnar" <mingo@...hat.com>, Borislav
 Petkov <bp@...en8.de>, <linux-perf-users@...r.kernel.org>, Peter Zijlstra
 <peterz@...radead.org>, Andi Kleen <andi.kleen@...el.com>, Xin Li
 <xin3.li@...el.com>, jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH v2 2/6] x86/irq: Extend NMI handler registration
 interface to include source

On Mon, 24 Jun 2024 16:16:52 -0700, Sohil Mehta <sohil.mehta@...el.com>
wrote:

> On 6/11/2024 9:54 AM, Jacob Pan wrote:
> > Add a source vector argument to register_nmi_handler() such that
> > designated NMI originators can leverage NMI source reporting feature.
> > For those who do not use NMI source reporting, 0 (unknown) is used as
> > the source vector. NMI source vectors (up to 16) are pre-defined.
> >   
> 
> What determines whether a source supports the new reporting vs some that
> don't? It might be useful to add that reasoning to the commit message as
> well.
> 
> I am guessing there is some connection to NMI_LOCAL based on
> use_nmi_source() definition but I am not sure.
Yes, this patch only enables NMI source reporting for local interrupts.
There is no use of MSIs delivered as NMI so far. Will add the rationale
here.

> Also, would it be worthwhile to split this patch into 2? One part that
> extents the register_nmi_handler() API and another that allocates the
> source vectors to certain sources.
Good point, will do.
> 
> > +static inline bool use_nmi_source(unsigned int type, struct nmiaction
> > *a) +{
> > +	return (cpu_feature_enabled(X86_FEATURE_NMI_SOURCE) &&
> > +		type == NMI_LOCAL && a->source_vec);
> > +}
> > +  
> 
> Sohil

Thanks,

Jacob