On Mon, Apr 04, 2016 at 11:10:56AM +1000, David Gibson wrote: > On Fri, Apr 01, 2016 at 12:28:31PM +0200, Paolo Bonzini wrote: > > > > > > On 01/04/2016 05:52, David Gibson wrote: > > > This seems like the right minimal fix in the qemu-2.6 timeframe to fix > > > the actual bug. However, longer term it seems like the correct thing > > > to do might be to set kvm_vcpu_dirty early in the reset path. Thoughts? > > > > Isn't it done already? vl.c does: > > > > pause_all_vcpus(); > > cpu_synchronize_all_states(); > > qemu_system_reset(VMRESET_REPORT); > > resume_all_vcpus(); > > > Huh.. now I'm really confused. Given this I would indeed have > expected kvm_vpcu_dirty to be set in the reset path, but that would > make the cpu_synchronize_state() causing the problem to act as a > no-op, so it shouldn't be causing the problem. > > Investigating...
Ok, I've found it.
So, if you reset the system after it's up and running, the fragment
above is indeed what will happen and I think everything will work
correct from there.
The problem occurs only on the very first reset in main() (vl.c:4624
as of de1d099): kvm_vcpu_dirty is false during this call.
Specifically, although kvm_vcpu_dirty was initialized to true in
kvm_vcpu_init(), it gets set to false in cpu_synchronize_post_init()
and never set true again before the qemu_system_reset().
Seems to me we either need a cpu_synchronize_all_states() before that
qemu_system_reset(), or we need to fold the
cpu_synchronize_all_states() right into qemu_system_reset() itself.
Opinion on which option is preferred?
>
> >
> > Thanks,
> >
> > Paolo
> >
> > > diff --git a/target-ppc/mmu-hash64.c b/target-ppc/mmu-hash64.c
> > > index 72c4ab5..caf41ce 100644
> > > --- a/target-ppc/mmu-hash64.c
> > > +++ b/target-ppc/mmu-hash64.c
> > > @@ -283,8 +283,6 @@ void ppc_hash64_set_external_hpt(PowerPCCPU *cpu,
> > > void *hpt, int shift,
> > > CPUPPCState *env = &cpu->env;
> > > Error *local_err = NULL;
> > >
> > > - cpu_synchronize_state(CPU(cpu));
> > > -
> > > if (hpt) {
> > > env->external_htab = hpt;
> > > } else {
> >
>
--
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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