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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Tue, 27 Sep 2016 20:18:38 +1000
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Subject: Re: [Qemu-devel] [PATCH v3 07/10] ppc/pnv: add XSCOM infrastructure
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To: =?ISO-8859-1?Q?C=E9dric?= Le Goater <clg@kaod.org>, David Gibson <david@gibson.dropbear.id.au>
Cc: qemu-ppc@nongnu.org, qemu-devel@nongnu.org

On Tue, 2016-09-27 at 11:30 +0200, C=C3=A9dric Le Goater wrote:
> On 09/27/2016 11:10 AM, C=C3=A9dric Le Goater wrote:
> >=20
> > >=20
> > > >=20
> > > > +#include <libfdt.h>
> > > > +
> > > > +static void xscom_complete(uint64_t hmer_bits)
> > > > +{
> > > > +=C2=A0=C2=A0=C2=A0=C2=A0CPUState *cs =3D current_cpu;
> > >=20
> > > Hmm.. is current_cpu a safe thing to use in the case of KVM or MTTC=
G?
> >=20
> > yes, as we are running under cpu_exec when doing this call.
>=20
> well, this is not true under the monitor.=C2=A0
>=20
> So we will have to come up with something to handle xscom read/writes=C2=
=A0
> from the monitor. Could we use first_cpu in that case ?=C2=A0

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,
>=20
> C.=C2=A0
>=20
> >=20
> > >=20
> > > >=20
> > > > +=C2=A0=C2=A0=C2=A0=C2=A0PowerPCCPU *cpu =3D POWERPC_CPU(cs);
> > > > +=C2=A0=C2=A0=C2=A0=C2=A0CPUPPCState *env =3D &cpu->env;
> > > > +
> > > > +=C2=A0=C2=A0=C2=A0=C2=A0cpu_synchronize_state(cs);
> > > > +=C2=A0=C2=A0=C2=A0=C2=A0env->spr[SPR_HMER] |=3D hmer_bits;
> > > > +
> > > > +=C2=A0=C2=A0=C2=A0=C2=A0/* XXX Need a CPU helper to set HMER, al=
so handle gneeration
> > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0* of HMIs
> > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0*/
> >=20
> > Ben,=C2=A0
> >=20
> > The CPU helper would be to replicate the value of the SPR_HMER in all
> > the threads of the core I guess ?=C2=A0
> >=20
> > Thanks,
> >=20
> > C.
> >=20