Re: [Qemu-devel] [Qemu-ppc] [PATCH 3/3] spapr: introduce a fixed IRQ number space

[Cédric Le Goater]

On 06/18/2018 11:54 AM, Greg Kurz wrote:
> On Mon, 18 Jun 2018 10:56:55 +0200
> Cédric Le Goater <address@hidden> wrote:
> 
>> [ ... ]
>>
>>>>> This is 4 irqs per PHB, hence up to 32 PHBs. Cool, we're currently
>>>>> limited to 31 PHBs.
>>>>>     
>>>>>> +#define SPAPR_IRQ_MSI        0x1100  /* Offset of the dynamic range 
>>>>>> covered    
>>>>>
>>>>> We only support dynamic MSIs with PCI, maybe rename to SPAPR_IRQ_PCI_MSI 
>>>>> ?    
>>>>
>>>> hmm, no. We could have CAPI devices there. remember ? ;)
>>>>  
>>>
>>> Well... OpenCAPI devices are exposed to the OS as PCI devices, so I'm not
>>> sure we need a CAPI specific range.  
>>
>> yes. so this range is common to all devices doing dynamic allocation
>> of IRQs. How should we call it ? 
>>
>>>>>> +                                      * by the bitmap allocator */    
>>>>>
>>>>> The range size is hence 1k (XICS_IRQS_SPAPR) for the time being.    
>>>>
>>>> in fact we could this bogus limit and use spapr->irq_map_nr now.
>>>>  
>>>
>>> "we could *missing verb* this bogus limit"... so I'm not sure to
>>> understand...  
>>
>> oups. We could use spapr->irq_map_nr instead of XICS_IRQS_SPAPR when
>> defining : 
>>
>>     _FDT(fdt_setprop_cell(fdt, bus_off, "ibm,pe-total-#msi", 
>> XICS_IRQS_SPAPR));
>>
>> in spapr_pci.c
>>
> 
> Ah... yeah, I've always found weird that all PHBs advertise the same number
> of available MSIs as the total number of irqs for the whole machine. And
> putting spapr->irq_map_nr looks weird all the same if all PHBs rely on the
> same bitmap actually.
> 
> I'm thinking of doing the other way around: keep XICS_IRQS_SPAPR in
> "ibm,pe-total-#msi" and have one XICS_IRQS_SPAPR sized bitmap per PHB.

That could be the place where to put the msi allocator.

C.