Re: [Xen-devel] [PATCH v3 06/15] xen/arm: vgic-v3: Set stride during domain initialization

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Mon, 2015-02-16 at 14:50 +0000, Julien Grall wrote:
> The stride may not be set if the hardware GIC is using the default
> layout. It happens on the Foundation model.
> 
> On GICv3, the default stride is 2 * 64K. Therefore it's possible to avoid
> checking at every redistributor MMIO access if the stride is not set.
> 
> Because domU uses a static stride configuration this only happens for
> dom0, so we can move this code in gicv_v3_init. Take the opportunity to move
> the stride setting a bit earlier because the loop to set regions will require
> the stride.
> 
> Also, use 2 * 64K rather than 128K and explain the reason.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>

Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

>     I wasn't not sure where to move this code. I find very confusion the
>     splitting between vgic and gicv. Maybe we should introduce a
>     hwdom_gicv_init and giccc_map callbacks. Then move most of the
>     initialization in the vgic one.

What is giccc? I'm not familiar enough with this code to rule on what
should go where. Perhaps Stefano has an opinion.

Ian.


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