Re: Why do we mark vpending table as non-shareable in GICR_VPENDBASER?

[Heyi Guo]

Thanks.

One more question about the cacheability of VPROPBASER, which is RaWb, while it is RaWaWb for PROPBASER. Any special reason for this?

Heyi


On 2019/5/9 15:58, Marc Zyngier wrote:
> On Thu, 09 May 2019 08:10:09 +0100,
> Heyi Guo <guoheyi@xxxxxxxxxx> wrote:
> > Hi Marc,
> >
> > We can see in its_vpe_schedule() the shareability bits of
> > GICR_VPENDBASER are set as non-shareable, But we set physical
> > PENDBASER as inner-shareable. Is there any special reason for doing
> > this? If it is because the vpending table is GICR specific, why
> > don't we do the same for physical pending table?
> That's a good question. They should have similar attributes.
>
> > We have not seen function issue with this setting, but a special
> > detector in our hardware warns us that there are non-shareable
> > requests sent out while some inner shareable cache entries still
> > present in the cache, and it may cause data inconsistent.
> The main issue with the inner-shareable attributes and the GIC is that
> nothing in the spec says that CPUs and GIC have to be in the same
> inner-shareable domain, as the system can have as many as you want.
>
> You obviously have built it with GICR in the same inner-shareability
> domain as the CPU. I'm happy to change the VPENDBASER attributes,
> given that the CPU has a mapping to that memory already, and that
> shouldn't affect systems where GICR isn't in the same inner shareable
> domain anyway.
>
> Thanks,
>
> 	M.