linux-kernel - RE: [PATCH v4] ACPI: AGDI: Add interrupt signaling mode support

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Message-ID:
 <OSAPR01MB766981DB17DEF8F3161321E0D5CCA@OSAPR01MB7669.jpnprd01.prod.outlook.com>
Date: Wed, 12 Nov 2025 09:18:18 +0000
From: "Kazuhiro Abe (Fujitsu)" <fj1078ii@...itsu.com>
To: 'Charles Mirabile' <cmirabil@...hat.com>
CC: "catalin.marinas@....com" <catalin.marinas@....com>, "Koichi Okuno
 (Fujitsu)" <fj2767dz@...itsu.com>, "guohanjun@...wei.com"
	<guohanjun@...wei.com>, "ilkka@...amperecomputing.com"
	<ilkka@...amperecomputing.com>, "lenb@...nel.org" <lenb@...nel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "lpieralisi@...nel.org"
	<lpieralisi@...nel.org>, "rafael@...nel.org" <rafael@...nel.org>,
	"sudeep.holla@....com" <sudeep.holla@....com>, "will@...nel.org"
	<will@...nel.org>
Subject: RE: [PATCH v4] ACPI: AGDI: Add interrupt signaling mode support

Hi Charlie,
Thank you for your comments.

> Hi All—
> 
> On Mon, Nov 10, 2025 at 07:38:17AM +0000, Kazuhiro Abe (Fujitsu) wrote:
> > Hi Will,
> >
> > > Hi Will,
> > >
> > > > [You don't often get email from will@...nel.org. Learn why this is
> > > > important at https://aka.ms/LearnAboutSenderIdentification ]
> > > >
> > > > On Mon, Oct 20, 2025 at 09:23:05PM +0800, Hanjun Guo wrote:
> > > > > On 2025/10/17 15:39, Kazuhiro Abe wrote:
> > > > > > AGDI has two types of signaling modes: SDEI and interrupt.
> > > > > > Currently, the AGDI driver only supports SDEI.
> > > > > > Therefore, add support for interrupt signaling mode The
> > > > > > interrupt vector is retrieved from the AGDI table, and call
> > > > > > panic function when an interrupt occurs.
> > > > > >
> > > > > > Reviewed-by: Ilkka Koskinen <ilkka@...amperecomputing.com>
> > > > > > Signed-off-by: Kazuhiro Abe <fj1078ii@...jp.fujitsu.com>
> > > > > > ---
> > > > > > Hanjun, I have addressed all your comments.
> > > > > > Please review them.
> > > > > >
> > > > > > v3->v4
> > > > > >   - Add a comment to the flags member.
> > > > > >   - Fix agdi_interrupt_probe.
> > > > > >   - Fix agdi_interrupt_remove.
> > > > > >   - Add space in struct initializsation.
> > > > > >   - Delete curly braces.
> > > > >
> > > > > Looks good to me,
> > > > >
> > > > > Acked-by: Hanjun Guo <guohanjun@...wei.com>
> > > >
> > > > I wasn't cc'd on the original patch but I couldn't figure out why
> > > > it uses IRQF_NO_AUTOEN when requesting the irq given that the
> > > > first thing it does is enable it.
> > >
> > > I misunderstood the usage of request_irq and enable_irq.
> > > Since there's no need to separate them, I will remove IRQF_NO_AUTOEN
> > > and the enable_irq call, and send v5.
> >
> > I found out when calling request_nmi, removing IRQF_NO_AUTOEN results
> in an error (-EINVAL).
> > Therefore, I would like to keep IRQF_NO_AUTOEN specified.
> > If you have any comments on this version, please let me know.
> 
> Could it be that this is just a bug in `request_nmi`? I see the following:
> 
> if (!desc || (irq_settings_can_autoenable(desc) &&
>     !(irqflags & IRQF_NO_AUTOEN)) ||
>     !irq_settings_can_request(desc) ||
>     WARN_ON(irq_settings_is_per_cpu_devid(desc)) ||
>     !irq_supports_nmi(desc))
>         return -EINVAL;
> 
> Perhaps there is just a missing `!` before `irq_settings_can_autoenable`.
> 
> As far as I can tell it has always been wrong - git blame points me to the original
> commit where that code was introduced:
> 
> b525903c254da ("genirq: Provide basic NMI management for interrupt lines")
> 
> I looked and the only two callers are using `IRQF_NO_AUTOEN` so I guess it
> just hasn't been noticed yet.
> 
> Happy to send a patch to fix it.

I noticed that commit (b525903c254da) log says:
>  Interrupt lines allocated for NMI delivery must be enabled/disabled through
>  enable_nmi/disable_nmi_nosync to keep their state consistent.

Similar comments also exist in the function comments of request_nmi().
So, I wonder if disabling auto-enabling for request_nmi() is a design choice.

As far as I can see, there is no fundamental reason to restrict the flag.
If we agree to remove the restriction for request_nmi(),  I'm willing to update this patch.
I'd like to know others' opinions.

Best Regards,
Kazuhiro Abe
> 
> >
> > Best Regards,
> > Kazuhiro Abe
> >
> > >
> > > Best Regards,
> > > Kazuhiro Abe
> > >
> > > >
> > > > Will
> 
> Best—Charlie