Re: [Qemu-devel] [PATCH v3 07/10] ppc/pnv: add XSCOM infrastructure

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Tue, 2016-09-27 at 11:30 +0200, Cédric Le Goater wrote:
> On 09/27/2016 11:10 AM, Cédric Le Goater wrote:
> > 
> > > 
> > > > 
> > > > +#include <libfdt.h>
> > > > +
> > > > +static void xscom_complete(uint64_t hmer_bits)
> > > > +{
> > > > +    CPUState *cs = current_cpu;
> > > 
> > > Hmm.. is current_cpu a safe thing to use in the case of KVM or MTTCG?
> > 
> > yes, as we are running under cpu_exec when doing this call.
> 
> well, this is not true under the monitor. 
> 
> So we will have to come up with something to handle xscom read/writes 
> from the monitor. Could we use first_cpu in that case ? 

Well, we'll need to find the chip etc... I think the XSCOM bridge (or bus)
should have special methods for the monitor that don't update HMER but
print out the status instead.

Cheers,
Ben.

> Thanks,
> 
> C. 
> 
> > 
> > > 
> > > > 
> > > > +    PowerPCCPU *cpu = POWERPC_CPU(cs);
> > > > +    CPUPPCState *env = &cpu->env;
> > > > +
> > > > +    cpu_synchronize_state(cs);
> > > > +    env->spr[SPR_HMER] |= hmer_bits;
> > > > +
> > > > +    /* XXX Need a CPU helper to set HMER, also handle gneeration
> > > > +     * of HMIs
> > > > +     */
> > 
> > Ben, 
> > 
> > The CPU helper would be to replicate the value of the SPR_HMER in all
> > the threads of the core I guess ? 
> > 
> > Thanks,
> > 
> > C.
> >