Access to remote XIVE2 units (was Re: [PATCH v9 0/7] Power11 support for QEMU [PowerNV])

["Cédric Le Goater" <clg@redhat.com>]

+ Glenn
+ Gautam

On 8/10/25 12:45, Aditya Gupta wrote:
> On 25/08/10 12:26PM, Aditya Gupta wrote:
>>> <...snip...>
>>
>> About the error, seems xive2 always expecting powernv10 chip, I will
>> have to rethink how should I use the same xive2 for powernv11.
>>
> 
> There's a type cast to Pnv10Chip in 'pnv_xive2_get_remote'.
> The cast is only temporarily used to get the 'PnvXive2' object in the
> Pnv10Chip.
> It's the only place in hw/intc/pnv_xive2.c assuming Pnv10Chip object.
> 
> Thinking to have a helper function to just return the 'PnvXive2' object
> inside the chip, given a 'PnvChip'.
> 
> Or the below change where we are adding another pointer in PnvChipClass:
> 
>      diff --git a/hw/intc/pnv_xive2.c b/hw/intc/pnv_xive2.c
>      index e019cad5c14c..9832be5fd297 100644
>      --- a/hw/intc/pnv_xive2.c
>      +++ b/hw/intc/pnv_xive2.c
>      @@ -110,8 +110,8 @@ static PnvXive2 *pnv_xive2_get_remote(uint32_t vsd_type, hwaddr fwd_addr)
>           int i;
>       
>           for (i = 0; i < pnv->num_chips; i++) {
>      -        Pnv10Chip *chip10 = PNV10_CHIP(pnv->chips[i]);
>      -        PnvXive2 *xive = &chip10->xive;
>      +        PnvChipClass *k = PNV_CHIP_GET_CLASS(pnv->chips[i]);
>      +        PnvXive2 *xive = k->intc_get(pnv->chips[i]);
>       
>               /*
>                * Is this the XIVE matching the forwarded VSD address is for this
> 
> Which one do you suggest ? Or should I look for another way ?
> 
> I am preferring the first way to have a helper, but both ways look hacky.

Any call to qdev_get_machine() in device model is at best
a modeling shortcut, most likely it is a hack :

   /*
    * Remote access to INT controllers. HW uses MMIOs(?). For now, a simple
    * scan of all the chips INT controller is good enough.
    */

So all these calls are suspicious :

   $ git grep qdev_get_machine hw/*/*pnv*
   hw/intc/pnv_xive2.c:    PnvMachineState *pnv = PNV_MACHINE(qdev_get_machine());
   hw/pci-host/pnv_phb.c:    PnvMachineState *pnv = PNV_MACHINE(qdev_get_machine());
   hw/pci-host/pnv_phb3.c:    PnvMachineState *pnv = PNV_MACHINE(qdev_get_machine());
   hw/ppc/pnv.c:    PnvMachineState *pnv = PNV_MACHINE(qdev_get_machine());
   hw/ppc/pnv.c:    PnvMachineState *pnv = PNV_MACHINE(qdev_get_machine());
   hw/ppc/pnv_chiptod.c:    PnvMachineState *pnv = PNV_MACHINE(qdev_get_machine());
   hw/ppc/pnv_chiptod.c:    PnvMachineState *pnv = PNV_MACHINE(qdev_get_machine());
   hw/ppc/pnv_lpc.c:    PnvMachineState *pnv = PNV_MACHINE(qdev_get_machine());

In the particular case of XIVE2, the solution is to rework
pnv_xive2_get_remote() like it was for P9. See b68147b7a5bf
("ppc/xive: Add support for the PC MMIOs").


Thanks,

C.