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

[Greg Kurz <groug@kaod.org>]

On Mon, 18 Jun 2018 13:31:26 +0200
Cédric Le Goater <clg@kaod.org> wrote:

> On 06/18/2018 11:54 AM, Greg Kurz wrote:
> > On Mon, 18 Jun 2018 10:56:55 +0200
> > Cédric Le Goater <clg@kaod.org> 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.
> 

Are you suggesting to move @irq_map and @irq_map_nr to sPAPRPHBState and
to have these setup during PHB realize ? I guess we could do that.

> C.