Re: [PATCH 10/35] irqchip/gic-v4.1: VPE table (aka GICR_VPROPBASER) allocation

[Zenghui Yu]

On 2019/9/26 23:57, Marc Zyngier wrote:
> On 26/09/2019 16:19, Zenghui Yu wrote:
> > On 2019/9/25 22:41, Marc Zyngier wrote:
> > > Indeed. The whole idea is that ITSs and RDs can share a vPE table if
> > > they are in the same affinity group (such as a socket, for example).
> > > This is what is missing from v4.0 where the ITS knows about vPEs, but
> > > doesn't know about residency. With that in place, the HW is able to do a
> > > lot more for us.
> >
> > Thanks for your education!
> >
> > I really want to know *how* does GICv4.1 ITS know about the vPE
> > residency (in hardware level)?
>
> Hey, I'm a SW guy, I don't design the hardware! ;-)
>
> > I can understand that Redistributor can easily achieve it by
> > VPENDBASER's Valid and vPEID field.  And it's necessary for ITS to
> > know the residency so that it can determine whether it's appropriate
> > to trigger default doorbell for vPE.  But I have no knowledge about
> > how can it be achieved in hardware details.
>
> My take is that the RD and the ITS can communicate over the shared
> table, hence my remark above about SVPET==0. But as I said, I'm not a HW
> guy.

;-) I should have asked our GIC engineers for these things.


Thanks,
zenghui