Re: [PATCH 2/3] genirq: Export NMI APIs

[Thomas Gleixner]

On Fri, Jul 31 2026 at 16:18, Doug Anderson wrote:
> On Thu, Jul 30, 2026 at 3:55 PM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>> > This seems reasonable to me. One thought I had was that we could
>> > possibly get by with fewer exported symbols by changing
>> > disable_nmi_nosync() and enable_nmi() to "static inline" functions in
>> > the header file. That being said, what Mayank has here feels slightly
>> > better to me.
>> >
>>
>> I don't claim to understand the NMI APIs used, but Sashiko's feedback
>> seems real to me. Someone who knows that code will need to confirm that
>> there are no unexpected pitfalls.
>
> Since Sashiko doesn't reply-to all, here's a link to its feedback:
>
> https://lore.kernel.org/all/20260730214758.DBD5E1F000E9@xxxxxxxxxxxxxxx/
>
> Indeed, it does look like legitimate feedback. While the problems are
> pre-existing, it is true that exporting as a module could widen the
> exposure because the code backing the NMI handler could now be
> unloaded.
>
> I did a little bit of AI analysis of the problem myself. As far as I
> can tell, it would be relatively safe to implement a synchronous
> "disable_nmi" by just calling "disable_irq", much like is done for
> other NMI functions. The caveat here is that it would only be safe on
> IRQ controllers that provided irq_get_irqchip_state(). This is because
> on NMI we don't set IRQD_IRQ_INPROGRESS and thus
> __synchronize_hardirq() will fall back to calling
> __irq_get_irqchip_state(). If any controllers supported NMI but
> _didn't_ support irq_get_irqchip_state(), we'd silently skip waiting
> for NMI completion. Maybe we could simply make it illegal for a
> controller to support NMI without irq_get_irqchip_state()?
>
> I guess maybe we need Thomas Gleixner to weigh in on this? Thomas:
> should this issue block Mayank's patch? Would you expect him to
> propose fixes as part of his series, or is this something you'd prefer
> to post patches for yourself?

Sorry, I did not pay attention as I was AFK and busy with bugs. I'll
have a look once the dust settles on my side (hopefully soonish).

Thanks,

        tglx