Re: [Qemu-devel] [PATCH] spapr: support CPU hotplug

[David Gibson <david@gibson.dropbear.id.au>]

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On Mon, Aug 26, 2013 at 02:24:49PM +0200, Alexander Graf wrote:
> 
> On 23.08.2013, at 13:30, Alexey Kardashevskiy wrote:
> 
> > PAPR+ requires two RTAS calls to be supported by the hypervisor in
> > order to allow hotplugging VCPUs from the guest. The "start-cpu" RTAS
> > call was already there but "stop-self" was not.
> > 
> > This adds the "stop-self" RTAS call.
> > 
> > Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> > ---
> > hw/ppc/spapr_rtas.c | 14 ++++++++++++++
> > 1 file changed, 14 insertions(+)
> > 
> > diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
> > index 394ce05..8a4cfa0 100644
> > --- a/hw/ppc/spapr_rtas.c
> > +++ b/hw/ppc/spapr_rtas.c
> > @@ -202,6 +202,19 @@ static void rtas_start_cpu(PowerPCCPU *cpu_, sPAPREnvironment *spapr,
> >     rtas_st(rets, 0, -3);
> > }
> > 
> > +static void rtas_stop_self(PowerPCCPU *cpu, sPAPREnvironment *spapr,
> > +                           uint32_t token, uint32_t nargs,
> > +                           target_ulong args,
> > +                           uint32_t nret, target_ulong rets)
> > +{
> > +    CPUState *cs = CPU(cpu);
> > +    CPUPPCState *env = &cpu->env;
> > +
> > +    cs->halted = 1;
> > +    env->msr = 0;
> 
> So this is here to make sure we don't accidentally get out of halted state by an interrupt on that vcpu. Could you please somehow make that part obvious? Either by adding a comment or by only explicitly masking DEC and EE and a comment :).
> 
> > +    cs->exit_request = 1;
> 
> This should probably be qemu_cpu_kick_self().

Uh, no, I don't think so.  This is there purely to make sure we exit
the inner loop, and actually test cpu_can_run() which will test
halted.  AFAICT qemu_cpu_kick_self() won't do anything similar.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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