Re: [PATCH] ppc/pnv: Create BMC devices only when defaults are enabled

[Cédric Le Goater]

On 4/4/20 11:44 PM, Nathan Chancellor wrote:
> Hi Cédric,
> 
> On Sat, Apr 04, 2020 at 05:36:55PM +0200, Cédric Le Goater wrote:
>> Commit e2392d4395dd ("ppc/pnv: Create BMC devices at machine init")
>> introduced default BMC devices which can be a problem when the same
>> devices are defined on the command line with :
>>
>>   -device ipmi-bmc-sim,id=bmc0 -device isa-ipmi-bt,bmc=bmc0,irq=10
>>
>> QEMU fails with :
>>
>>   qemu-system-ppc64: error creating device tree: node: FDT_ERR_EXISTS
>>
>> Use defaults_enabled() when creating the default BMC devices to let
>> the user provide its own BMC devices using '-nodefaults'. If no BMC
>> device are provided, output a warning but let QEMU run as this is a
>> supported configuration. However, when multiple BMC devices are
>> defined, stop QEMU with a clear error as the results are unexpected.
>>
>> Fixes: e2392d4395dd ("ppc/pnv: Create BMC devices at machine init")
>> Reported-by: Nathan Chancellor <address@hidden>
>> Signed-off-by: Cédric Le Goater <address@hidden>
> 
> This fixes my issue when -nodefaults is passed and that does not regress
> QEMU 3.1.0 or 4.2.0. Thank you for the quick fix!
> 
> Tested-by: Nathan Chancellor <address@hidden>
> 
> A few comments inline.
> 
>> ---
>>  include/hw/ppc/pnv.h |  2 ++
>>  hw/ppc/pnv.c         | 32 ++++++++++++++++++++++++++-----
>>  hw/ppc/pnv_bmc.c     | 45 ++++++++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 74 insertions(+), 5 deletions(-)
>>
>> diff --git a/include/hw/ppc/pnv.h b/include/hw/ppc/pnv.h
>> index fb4d0c0234b3..d4b0b0e2ff71 100644
>> --- a/include/hw/ppc/pnv.h
>> +++ b/include/hw/ppc/pnv.h
>> @@ -241,6 +241,8 @@ struct PnvMachineState {
>>  void pnv_dt_bmc_sensors(IPMIBmc *bmc, void *fdt);
>>  void pnv_bmc_powerdown(IPMIBmc *bmc);
>>  IPMIBmc *pnv_bmc_create(PnvPnor *pnor);
>> +IPMIBmc *pnv_bmc_find(Error **errp);
>> +void pnv_bmc_set_pnor(IPMIBmc *bmc, PnvPnor *pnor);
>>  
>>  /*
>>   * POWER8 MMIO base addresses
>> diff --git a/hw/ppc/pnv.c b/hw/ppc/pnv.c
>> index ac83b8698b8e..a3b7a8d0ff32 100644
>> --- a/hw/ppc/pnv.c
>> +++ b/hw/ppc/pnv.c
>> @@ -573,10 +573,29 @@ static void pnv_powerdown_notify(Notifier *n, void 
>> *opaque)
>>  
>>  static void pnv_reset(MachineState *machine)
>>  {
>> +    PnvMachineState *pnv = PNV_MACHINE(machine);
>> +    IPMIBmc *bmc;
>>      void *fdt;
>>  
>>      qemu_devices_reset();
>>  
>> +    /*
>> +     * The machine should provide by default an internal BMC simulator.
>> +     * If not, try to use the BMC device that was provided on the command
>> +     * line.
>> +     */
>> +    bmc = pnv_bmc_find(&error_fatal);
>> +    if (!pnv->bmc) {
>> +        if (!bmc) {
>> +            warn_report("machine has no BMC device. Use '-device "
>> +                        "ipmi-bmc-sim,id=bmc0 -device 
>> isa-ipmi-bt,bmc=bmc0,irq=10' "
>> +                        "to define one");
> 
> If I pass no -device flags + -nodefaults, I don't see this message. Is
> that expected?

yes. Because the machine instantiates the default BMC devices.

> 
>> +        } else {
>> +            pnv_bmc_set_pnor(bmc, pnv->pnor);
>> +            pnv->bmc = bmc;
>> +        }
>> +    }
>> +
>>      fdt = pnv_dt_create(machine);
>>  
>>      /* Pack resulting tree */
>> @@ -835,9 +854,6 @@ static void pnv_init(MachineState *machine)
>>      }
>>      g_free(chip_typename);
>>  
>> -    /* Create the machine BMC simulator */
>> -    pnv->bmc = pnv_bmc_create(pnv->pnor);
>> -
>>      /* Instantiate ISA bus on chip 0 */
>>      pnv->isa_bus = pnv_isa_create(pnv->chips[0], &error_fatal);
>>  
>> @@ -847,8 +863,14 @@ static void pnv_init(MachineState *machine)
>>      /* Create an RTC ISA device too */
>>      mc146818_rtc_init(pnv->isa_bus, 2000, NULL);
>>  
>> -    /* Create the IPMI BT device for communication with the BMC */
>> -    pnv_ipmi_bt_init(pnv->isa_bus, pnv->bmc, 10);
>> +    /*
>> +     * Create the machine BMC simulator and the IPMI BT device for
>> +     * communication with the BMC
>> +     */
>> +    if (defaults_enabled()) {
>> +        pnv->bmc = pnv_bmc_create(pnv->pnor);
>> +        pnv_ipmi_bt_init(pnv->isa_bus, pnv->bmc, 10);
>> +    }
>>  
>>      /*
>>       * OpenPOWER systems use a IPMI SEL Event message to notify the
>> diff --git a/hw/ppc/pnv_bmc.c b/hw/ppc/pnv_bmc.c
>> index 8863354c1c08..4e018b8b70e4 100644
>> --- a/hw/ppc/pnv_bmc.c
>> +++ b/hw/ppc/pnv_bmc.c
>> @@ -213,6 +213,18 @@ static const IPMINetfn hiomap_netfn = {
>>      .cmd_handlers = hiomap_cmds
>>  };
>>  
>> +
>> +void pnv_bmc_set_pnor(IPMIBmc *bmc, PnvPnor *pnor)
>> +{
>> +    object_ref(OBJECT(pnor));
>> +    object_property_add_const_link(OBJECT(bmc), "pnor", OBJECT(pnor),
>> +                                   &error_abort);
>> +
>> +    /* Install the HIOMAP protocol handlers to access the PNOR */
>> +    ipmi_sim_register_netfn(IPMI_BMC_SIMULATOR(bmc), IPMI_NETFN_OEM,
>> +                            &hiomap_netfn);
>> +}
>> +
>>  /*
>>   * Instantiate the machine BMC. PowerNV uses the QEMU internal
>>   * simulator but it could also be external.
>> @@ -232,3 +244,36 @@ IPMIBmc *pnv_bmc_create(PnvPnor *pnor)
>>  
>>      return IPMI_BMC(obj);
>>  }
>> +
>> +typedef struct ForeachArgs {
>> +    const char *name;
>> +    Object *obj;
>> +} ForeachArgs;
>> +
>> +static int bmc_find(Object *child, void *opaque)
>> +{
>> +    ForeachArgs *args = opaque;
>> +
>> +    if (object_dynamic_cast(child, args->name)) {
>> +        if (args->obj) {
>> +            return 1;
>> +        }
>> +        args->obj = child;
>> +    }
>> +    return 0;
>> +}
>> +
>> +IPMIBmc *pnv_bmc_find(Error **errp)
>> +{
>> +    ForeachArgs args = { TYPE_IPMI_BMC_SIMULATOR, NULL };
>> +    int ret;
>> +
>> +    ret = object_child_foreach_recursive(object_get_root(), bmc_find, 
>> &args);
>> +    if (ret) {
>> +        error_setg(errp, "machine should have only one BMC device. "
>> +                   "Use '-nodefaults'");
> 
> When passing the -device flags in the commit message as I did in my
> original command without -nodefaults, I still see the
> 
> qemu-system-ppc64: error creating device tree: node: FDT_ERR_EXISTS
> 
> message. Is that expected?
object_child_foreach_recursive() is broken. Here is the fix :

   http://patchwork.ozlabs.org/patch/1266419/

Sorry. I should have copied you.

But there are other ways to find multiple instances of the same type. 
May be we will need to rework that part a bit.

Thanks,

C.

> 
>> +        return NULL;
>> +    }
>> +
>> +    return args.obj ? IPMI_BMC(args.obj) : NULL;
>> +}
>> -- 
>> 2.25.1
>>