Re: [PATCH 3/6] ppc/pegasos2: Implement get-time-of-day RTAS function with VOF

[BALATON Zoltan]

On Fri, 15 Oct 2021, David Gibson wrote:
> On Thu, Oct 14, 2021 at 09:50:19PM +0200, BALATON Zoltan wrote:
> > This is needed for Linux to access RTC time.
> >
> > Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
> > ---
> >  hw/ppc/pegasos2.c | 25 +++++++++++++++++++++++++
> >  1 file changed, 25 insertions(+)
> >
> > diff --git a/hw/ppc/pegasos2.c b/hw/ppc/pegasos2.c
> > index a1dd1f6752..a9e3625f56 100644
> > --- a/hw/ppc/pegasos2.c
> > +++ b/hw/ppc/pegasos2.c
> > @@ -31,6 +31,8 @@
> >  #include "sysemu/kvm.h"
> >  #include "kvm_ppc.h"
> >  #include "exec/address-spaces.h"
> > +#include "qom/qom-qobject.h"
> > +#include "qapi/qmp/qdict.h"
> >  #include "trace.h"
> >  #include "qemu/datadir.h"
> >  #include "sysemu/device_tree.h"
> > @@ -369,6 +371,29 @@ static target_ulong pegasos2_rtas(PowerPCCPU *cpu, 
> > Pegasos2MachineState *pm,
> >          return H_PARAMETER;
> >      }
> >      switch (token) {
> > +    case RTAS_GET_TIME_OF_DAY:
> > +    {
> > +        QObject *qo = object_property_get_qobject(qdev_get_machine(),
> > +                                                  "rtc-time", &error_fatal);
> > +        QDict *qd = qobject_to(QDict, qo);
> > +
> > +        if (nargs != 0 || nrets != 8 || !qd) {
> > +            stl_be_phys(as, rets, -1);
> > +            qobject_unref(qo);
> > +            return H_PARAMETER;
> > +        }
> > +
> > +        stl_be_phys(as, rets, 0);
> > +        stl_be_phys(as, rets + 4, qdict_get_int(qd, "tm_year") + 1900);
> > +        stl_be_phys(as, rets + 8, qdict_get_int(qd, "tm_mon") + 1);
> > +        stl_be_phys(as, rets + 12, qdict_get_int(qd, "tm_mday"));
> > +        stl_be_phys(as, rets + 16, qdict_get_int(qd, "tm_hour"));
> > +        stl_be_phys(as, rets + 20, qdict_get_int(qd, "tm_min"));
> > +        stl_be_phys(as, rets + 24, qdict_get_int(qd, "tm_sec"));
>
> Doing a separate dictionary lookup for every component seems like it
> might be pretty expensive.  You might want to look at how spapr does
> this.

This is the only short way I could find to read the RTC the same way as 
the guest or firmware would. I wasn't sure because the rtc model has an 
update rtc function that it calls before reads to set the values but that 
looks like doing the same as spapr does so I'll send another patch 
replacing this with that then.

Thanks,
BALATON Zoltan

> However, you're maintainer for pegasos, so really it's your call -
> applied, thanks.
>
> > +        stl_be_phys(as, rets + 28, 0);
> > +        qobject_unref(qo);
> > +        return H_SUCCESS;
> > +    }
> >      case RTAS_READ_PCI_CONFIG:
> >      {
> >          uint32_t addr, len, val;