Re: [Xen-devel] [PATCH for-4.6] xen/arm: vgic-v2: Map the GIC virtual CPU interface with the correct size

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Mon, 2015-09-21 at 13:28 +0100, Julien Grall wrote:
> Hi Ian,
> 
> On 21/09/15 12:54, Ian Campbell wrote:
> > On Fri, 2015-09-18 at 09:53 +0100, Ian Campbell wrote:
> > > On Thu, 2015-09-17 at 19:00 +0100, Julien Grall wrote:
> > > > On GICv2, the GIC virtual CPU interface is at minimum 8KB. Due some
> > > > to
> > > > some necessary quirk for GIC using 64KB stride, we are mapping the
> > > > region in 2 time.
> > > > The first mapping is 4KB and the second one is 8KB, i.e 12KB in
> > > > total.
> > > > Although the minimum supported size (and widely used) is 8KB. This
> > > > means
> > > > that we are mapping 4KB more to any guest using GICv2.
> > > > 
> > > > While this looks scary at first glance, the GIC virtual CPU
> > > > interface
> > > > is
> > > > most frequently at the end the GIC I/O region. So we will most
> > > > likely
> > > > map an an unused I/O region or a mirrored version of GICV for
> > > > platform
> > > > using 64KB stride.
> > > > 
> > > > Nonetheless, fix the second mapping to only map 4KB.
> > > > 
> > > > Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> > > 
> > > Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> > > 
> > > > ---
> > > > 
> > > > This is a candidate for Xen 4.6 and backport to Xen 4.5.
> > > 
> > > I concur and with Wei not being around I shall plan to apply later
> > > today
> > > unless there are objections.
> > 
> > I got distracted. Now applied to staging and staging-4.6 now and noted
> > for
> > later application to 4.5
> 
> It won't apply cleanly for Xen 4.5, this code was living in the gic
> driver. I will send a backport patch for it.

Thanks.


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