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

On 19/02/15 15:58, Ian Campbell wrote:
> 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.

I think the name of giccc what bad here. What I wanted to mean is
splitting the current gicv_setup code in 2 parts:
        - Mapping GICV to the guest
        - Set up the hwdom information

This will bring a better partition to the code and bring GICv2 on GICv3
support more quickly.

I will talk with Stefano about this possibility.


Julien Grall

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