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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2015-02-03 at 13:14 +0000, Julien Grall wrote:
> On 02/02/15 17:41, Ian Campbell wrote:
> > 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.
> 
> Shall I clarify the commit message for this bit?

It can't hurt.

Ian.



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