Re: [Xen-devel] [PATCH v4 1/4] xen/arm: vgic-v2: Report the correct GICC size to the guest

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Fri, 2015-10-23 at 14:34 +0100, Julien Grall wrote:
> Hi Ian,
> 
> On 23/10/15 14:28, Ian Campbell wrote:
> > On Thu, 2015-10-08 at 19:23 +0100, Julien Grall wrote:
> > > The GICv2 DT node is usually used by the guest to know the
> > > address/size
> > > of the regions (GICD, GICC...) to map into their virtual memory.
> > > 
> > > While the GICv2 spec requires the size of the GICC to be 8KB, we
> > > correctly do an 8KB stage-2 mapping but errornously report 256 in the
> > > device tree (based on GUEST_GICC_SIZE).
> > 
> > "erroneously"
> > 
> > > 
> > > I bet we didn't see any issue so far because all the registers except
> > > GICC_DIR lives in the first 256 bytes of the GICC region and all the
> > > guest
> > 
> > "guests"
> > 
> > > I have seen so far are driving the GIC with GICC_CTLR.EIOmode =
> > > 0.
> > > 
> > > Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> > 
> > Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> > 
> > (typo's fixable on commit).
> 
> Thank you!
> 
> > > ---
> > >     This patch is a good candidate to backport for Xen 4.6 - 4.4.
> > >     Without it a guest relying on the DT can't use GICC_DIR.
> > 
> > Noted, but just to check: This patch (and none of the other fixes in
> > this
> > series) are all which are required for a guest to be able to use
> > GICC_DIR,
> > right?
> 
> Correct. BTW, I forgot to mention that this patch may not apply cleanly
> on Xen 4.4 as rearranged the guest memory address space in Xen 4.5.

I'd be inclined not to bother with it for 4.4 at this juncture then.

Ian.

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