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

[Greg Kurz]

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 ?

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