Subject: Re: [kvm-unit-tests PATCH v9 14/31] powerpc: Remove broken SMP exception stack setup

From: "Nicholas Piggin" <[email-masked]>
Date: Tue, 04 Jun 2024 15:13:26 +1000

On Mon Jun 3, 2024 at 7:30 PM AEST, Thomas Huth wrote:
> On 04/05/2024 14.28, Nicholas Piggin wrote:
> > The exception stack setup does not work correctly for SMP, because
> > it is the boot processor that calls cpu_set() which sets SPRG2 to
> > the exception stack, not the target CPU itself. So secondaries
> > never got their SPRG2 set to a valid exception stack.
>
> So secondary CPUs currently must not run into any exceptions?

Yes, at the moment. It was broken anyway.

Patch 16 creates a proper environment for secondaries, including
taking interrupts.

Thanks,
Nick

>
> > Remove the SMP code and just set an exception stack for the boot
> > processor. Make the stack 64kB while we're here, to match the
> > size of the regular stack.
> > 
> > Signed-off-by: Nicholas Piggin <[email-masked]>
> > ---
> >   lib/powerpc/setup.c | 16 ++++++++--------
> >   1 file changed, 8 insertions(+), 8 deletions(-)
>
> Reviewed-by: Thomas Huth <[email-masked]>