Re: [Xen-devel] [PATCH v5 21/21] xen/arm: check for GICv3 platform support

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2014-06-16 at 16:37 +0100, Julien Grall wrote:
> On 06/16/2014 04:28 PM, Vijay Kilari wrote:
> > On Fri, Jun 13, 2014 at 4:21 AM, Julien Grall <julien.grall@xxxxxxxxxx> 
> > wrote:
> >> On 12/06/14 14:36, vijay.kilari@xxxxxxxxx wrote:
> >>>
> >>> From: Vijaya Kumar K <Vijaya.Kumar@xxxxxxxxxxxxxxxxxx>
> >>>
> >>> ID_AA64PFR0_EL1 register provides information about GIC support.
> >>> Check for this register in GICv3 driver.
> >>>
> >>> Also print GICv3 support information in boot log
> >>
> >>
> >> We already have a GICv3 node in the device tree. Why do we need to check
> >> that GICv3 is effectively support by board?
> >>
> >> We rely on the user provide us a correct device tree, so I don't think this
> >> patch is helpful...
> > 
> > GICv3 driver is compiled for arm64 alone. Assume that platform does not 
> > support
> > GICv3 and DT is passed with GICv3 info. In such scenario this patch helps.
> 
> I think this is pointless, lots of things (worst than trying to poke a
> GICv3 on a GICv2 platform) can happen on Xen and Linux if the user fails
> to give a valid device tree.
> 
> IHMO, it's safe to assume that the user will provide a device tree with
> valid devices...

Given that Vijay has already written the code and that it's pretty
unintrusive it seems like there is no downside to having a meaningful
error message if gicv3 isn't present.

Ian.


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