Re: [PATCH qemu] spapr: Force 32bit when resetting a core

[Cédric Le Goater]

On 1/7/22 14:39, Greg Kurz wrote:
> On Fri, 7 Jan 2022 23:19:03 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
>
> > On Fri, Jan 07, 2022 at 12:57:47PM +0100, Greg Kurz wrote:
> > > On Fri, 7 Jan 2022 18:24:23 +1100
> > > Alexey Kardashevskiy <aik@ozlabs.ru> wrote:
> > >
> > > > "PowerPC Processor binding to IEEE 1275" says in
> > > > "8.2.1. Initial Register Values" that the initial state is defined as
> > > > 32bit so do it for both SLOF and VOF.
> > > >
> > > > This should not cause behavioral change as SLOF switches to 64bit very
> > > > early anyway.
> > >
> > > Only one CPU goes through SLOF. What about the other ones, including
> > > hot plugged CPUs ?
> >
> > Those will be started by the start-cpu RTAS call which has its own
> > semantics.
>
> Ah indeed, there's code in linux/arch/powerpc/kernel/head_64.S to switch
> secondaries to 64bit... but then, as noted by Cedric, ppc_cpu_reset(),
> which is called earlier sets MSR_SF but the changelog of commit 8b9f2118ca40
> doesn't provide much details on the motivation. Any idea ?

I found some reference to the commit here but it doesn't seem
to be the root cause :

 https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1723914

Thanks,

C.