Re: [Xen-devel] [PATCH 05/10] xen/arm: vgic-v3: Document the current restrictions

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2015-01-20 at 17:49 +0000, Julien Grall wrote:

> >>     - A processor can only access his own redistributor. For buggy
> >>     assumption, the current code bank the redistributors MMIO.
> > 
> > What assumption? It's not clear if you mean that a foreign redistributor
> > should not be accessible and is, or if it should be accessible and
> > isn't.
> 
> Every redistributor (one per processor) are mapped in distinct MMIO region.
> 
> Unlike the distributor, the redistributor is not banked.

Understood.

> Our current implementation (see vgic_v3_rdistr_mmio_write) consider that
> the redistributor is banked and replicate n-times in the memory.

IOW instead of having e.g. 8 individual redistributors each vcpu sees
it's own redistributor 8 times. That does seem a bit dubious.

> If you give a look to the redistributor iniatialization (see Xen and
> Linux GICv3 code). The code will go through all the redistributors and
> check GICR_TYPER to see if the processor is associated to this
> redistributor.
> 
> I'm not sure how the redistributor should behave if it's accessed by
> another processor.

Please can you find a spec reference and include it in the clarified
version of this item.

> But I'm sure it's wrong to bank it.

Seems likely, but answering the above Q would probably decide this one
way or another too.


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