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

From: Mukesh Ojha
Date: Tue Jan 03 2023 - 11:45:24 EST


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.