Re: [Qemu-devel] [PATCH v5 07/16] spapr_rtas: add ibm, configure-connector RTAS interface

[Michael Roth <mdroth@linux.vnet.ibm.com>]

Quoting David Gibson (2015-02-24 00:40:32)
> On Mon, Feb 16, 2015 at 08:27:43AM -0600, Michael Roth wrote:
> > This interface is used to fetch an OF device-tree nodes that describes a
> > newly-attached device to guest. It is called multiple times to walk the
> > device-tree node and fetch individual properties into a 'workarea'/buffer
> > provided by the guest.
> > 
> > The device-tree is generated by QEMU and passed to an sPAPRDRConnector during
> > the initial hotplug operation, and the state of these RTAS calls is tracked by
> > the sPAPRDRConnector. When the last of these properties is successfully
> > fetched, we report as special return value to the guest and transition
> > the device to a 'configured' state on the QEMU/DRC side.
> > 
> > See docs/specs/ppc-spapr-hotplug.txt for a complete description of
> > this interface.
> > 
> > Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
> > ---
> >  hw/ppc/spapr_rtas.c | 81 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 81 insertions(+)
> > 
> > diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
> > index f80beb2..b8551b0 100644
> > --- a/hw/ppc/spapr_rtas.c
> > +++ b/hw/ppc/spapr_rtas.c
> > @@ -418,6 +418,85 @@ static void rtas_get_sensor_state(PowerPCCPU *cpu, sPAPREnvironment *spapr,
> >      rtas_st(rets, 1, entity_sense);
> >  }
> >  
> > +/* configure-connector work area offsets, int32_t units for field
> > + * indexes, bytes for field offset/len values.
> > + *
> > + * as documented by PAPR+ v2.7, 13.5.3.5
> > + */
> > +#define CC_IDX_NODE_NAME_OFFSET 2
> > +#define CC_IDX_PROP_NAME_OFFSET 2
> > +#define CC_IDX_PROP_LEN 3
> > +#define CC_IDX_PROP_DATA_OFFSET 4
> > +#define CC_VAL_DATA_OFFSET ((CC_IDX_PROP_DATA_OFFSET + 1) * 4)
> > +#define CC_WA_LEN 4096
> > +
> > +static void rtas_ibm_configure_connector(PowerPCCPU *cpu,
> > +                                         sPAPREnvironment *spapr,
> > +                                         uint32_t token, uint32_t nargs,
> > +                                         target_ulong args, uint32_t nret,
> > +                                         target_ulong rets)
> > +{
> > +    uint64_t wa_addr = ((uint64_t)rtas_ld(args, 1) << 32) | rtas_ld(args, 0);
> 
> You need to check nargs and nret first.

Could've sworn I'd fixed all those cases. Will make sure to take care of it on
the next one.

> 
> > +    uint64_t wa_offset;
> > +    uint32_t drc_index;
> > +    sPAPRDRConnector *drc;
> > +    sPAPRDRConnectorClass *drck;
> > +    sPAPRDRCCResponse resp;
> > +    const struct fdt_property *prop = NULL;
> > +    char *prop_name = NULL;
> > +    int prop_len, rc;
> > +
> > +    drc_index = rtas_ld(wa_addr, 0);
> > +    drc = spapr_dr_connector_by_index(drc_index);
> > +    if (!drc) {
> > +        DPRINTF("rtas_ibm_configure_connector: invalid sensor/DRC index: %xh\n",
> > +                drc_index);
> > +        rc = RTAS_OUT_PARAM_ERROR;
> > +        goto out;
> > +    }
> > +    drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
> > +    resp = drck->configure_connector(drc, &prop_name, &prop, &prop_len);
> 
> You may have answered this last time round, but if so I forgot the
> reason.
> 
> Why does the awkward iteration need to go down to the drck callback?
> Coudln't the drck callback part just supply the fdt fragment blob,
> then have generic code which streams it out via iteration?
> 
> Obviously we have to support the horrid PAPR interface, but it would
> be nice to confine the PAPR derived horridness to as small an area as
> we can.

That horrid interface percolates all the way up the QEMU stack,
unfortunately :)

Upon successfully having it's device tree node received, a DRC transitions
to a 'configured' state that's defined in the DR state machine (PAPR+ 13.4).

We need to track that state, since it's used to differentiate between
a case where a device is set to 'isolated' as part of entity-sense/device
configuration, as opposed to 'isolated' as part the unplug path. The
overlap between the 2 can occur if we do device_add followed by an immediate
device_del, but since the 'configured' transition must occur before the latter,
it becomes unambiguous.

It's also possible that a guest might be reset in the middle of a series of
calls to configure-connector, in which case that state needs to be reset. This
is currently handled by sPAPRDRConnector's reset hook, so if we moved that
aspect out I think we'd need to wire up a reset hook for the configure-connector
state, which is kinda messy. We'd also need a list of some sort, keyed by
the DRC indexes, to handle the subsequent call-per-iteration's (no guarantee
only one device configuration is 'in-flight' at a time), so we end up
duplicating a lot of tracking/functionality.

> 
> 
> > +    switch (resp) {
> > +    case SPAPR_DR_CC_RESPONSE_NEXT_CHILD:
> > +        /* provide the name of the next OF node */
> > +        wa_offset = CC_VAL_DATA_OFFSET;
> > +        rtas_st(wa_addr, CC_IDX_NODE_NAME_OFFSET, wa_offset);
> > +        rtas_st_buffer_direct(wa_addr + wa_offset, CC_WA_LEN - wa_offset,
> > +                              (uint8_t *)prop_name, strlen(prop_name) + 1);
> > +        break;
> > +    case SPAPR_DR_CC_RESPONSE_NEXT_PROPERTY:
> > +        /* provide the name of the next OF property */
> > +        wa_offset = CC_VAL_DATA_OFFSET;
> > +        rtas_st(wa_addr, CC_IDX_PROP_NAME_OFFSET, wa_offset);
> > +        rtas_st_buffer_direct(wa_addr + wa_offset, CC_WA_LEN - wa_offset,
> > +                              (uint8_t *)prop_name, strlen(prop_name) + 1);
> > +
> > +        /* provide the length and value of the OF property. data gets placed
> > +         * immediately after NULL terminator of the OF property's name string
> > +         */
> > +        wa_offset += strlen(prop_name) + 1,
> > +        rtas_st(wa_addr, CC_IDX_PROP_LEN, prop_len);
> > +        rtas_st(wa_addr, CC_IDX_PROP_DATA_OFFSET, wa_offset);
> > +        rtas_st_buffer_direct(wa_addr + wa_offset, CC_WA_LEN - wa_offset,
> > +                              (uint8_t *)((struct fdt_property *)prop)->data,
> > +                              prop_len);
> > +        break;
> > +    case SPAPR_DR_CC_RESPONSE_PREV_PARENT:
> > +    case SPAPR_DR_CC_RESPONSE_ERROR:
> > +    case SPAPR_DR_CC_RESPONSE_SUCCESS:
> > +        break;
> > +    default:
> > +        /* drck->configure_connector() should not return anything else */
> > +        g_assert(false);
> > +    }
> > +
> > +    rc = resp;
> > +out:
> > +    g_free(prop_name);
> > +    rtas_st(rets, 0, rc);
> > +}
> > +
> >  static struct rtas_call {
> >      const char *name;
> >      spapr_rtas_fn fn;
> > @@ -551,6 +630,8 @@ static void core_rtas_register_types(void)
> >                          rtas_set_indicator);
> >      spapr_rtas_register(RTAS_GET_SENSOR_STATE, "get-sensor-state",
> >                          rtas_get_sensor_state);
> > +    spapr_rtas_register(RTAS_IBM_CONFIGURE_CONNECTOR, "ibm,configure-connector",
> > +                        rtas_ibm_configure_connector);
> >  }
> >  
> >  type_init(core_rtas_register_types)
> 
> -- 
> 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