Re: [PATCH v2 20/20] ppc: propagate the calling conventions change down to csum_partial_copy_generic()

[Jason A. Donenfeld]

On Thu, Oct 15, 2020 at 12:51 AM Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> On Wed, Oct 14, 2020 at 3:27 PM Jason A. Donenfeld <Jason@xxxxxxxxx> wrote:
> >
> > This patch is causing crashes in WireGuard's CI over at
> > https://www.wireguard.com/build-status/ . Apparently sending a simple
> > network packet winds up triggering refcount_t's warn-on-saturate code. I
>
> Ouch.
>
> The C parts look fairly straightforward, and I don't see how they
> could cause that odd refcount issue.
>
> So I assume it's the low-level asm code conversion that is buggy. And
> it's apparently the 32-bit conversion, since your ppc64 status looks
> fine.
>
> I think it's this instruction:
>
>         addi    r1,r1,16
>
> that should be removed from the function exit, because Al removed the
>
> -       stwu    r1,-16(r1)

I just tried that about a minute ago, and indeed that seems to be
what's up. Problem goes away without it. I'll send a patch shortly.

Jason