Re: Query about IPI as NMI (pseudo-NMI) support patches

[Mukesh Ojha]

Hi,

Thanks for your reply.

On 1/2/2023 10:41 PM, Marc Zyngier wrote:
> Hi Mukesh,
>
> On Mon, 02 Jan 2023 16:44:59 +0000,
> Mukesh Ojha <quic_mojha@xxxxxxxxxxx> wrote:
> > Hi Marc,
> >
> > I was looking similar support mentioned in below patch series.
> >
> > https://lore.kernel.org/lkml/CAFA6WYO0+LQ=mB1spCstt0cNZ0G+sZu_+Wrv6BKSeXqF5SRq4A@xxxxxxxxxxxxxx/#t
> >
> > Wanted to check if there is chance of these patches to land in
> > mainline ?
>
> I certainly have no intention to merge it as is, specially as there is
> no good usage model for it other than "but think of debug!".
>
> We have exactly *one* SGI left. If we are going to lose it over such a
> feature, I'd want a description of how we are going to share it
> between potential users, and how we claw some currently used SGIs
> back.


But, looks like patch will fail if SGI is not available.

https://lore.kernel.org/lkml/1604317487-14543-4-git-send-email-sumit.garg@xxxxxxxxxx/



set_smp_ipi_range(base_sgi, 8);

+	if (n > nr_ipi)
+		set_smp_dynamic_ipi(ipi_base + nr_ipi);
+

So, static SGI allocation still has higher priority than dynamic one.
Would you be accepting if we keep it under some CONFIG_ARM64_IPI_NMI_DEBUG ?

-Mukesh
> Until then, this is a proof of concept, and not much else.
>
> Thanks,
>
> 	M.