Re: [Xen-devel] [PATCH v2 11/15] xen/arm: vgic-v2: Correctly handle RAZ/WI registers

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2015-02-02 at 17:08 +0000, Julien Grall wrote:
> On 02/02/15 16:50, Ian Campbell wrote:
> > On Mon, 2015-02-02 at 16:36 +0000, Julien Grall wrote:
> >> Hi Ian,
> >>
> >> On 02/02/15 16:02, Ian Campbell wrote:
> >>> On Thu, 2015-01-29 at 18:25 +0000, Julien Grall wrote:
> >>>> Some of the registers are accessible via multiple size (see 
> >>>> GICD_IPRIORITYR*).
> >>>
> >>> They are byte accessible, but are they half word accessible? I suspect
> >>> not.
> >>
> >> Only byte accessible.
> > 
> > I think we might need a read_as_zero_8_32 then, i.e. explicitly list the
> > sizes which are allowed, and perhaps omit the un-suffixed version for so
> > it's clear exactly what is what, although that might be more churn than
> > you want to have here.
> 
> Hmmm, why? I was talking for registers defined in the spec. We don't
> know if reserved/implementation defined registers will allow half-word
> access.
> 
> The un-suffixed version is there when we don't need to check the size
> because it has already been done. It seems pointless to check it again.

I'd forgotten the existing check was there, yes it does make sense to
use it in this case.

Ian.


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