Re: [Xen-devel] [PATCH 2/6] xen/arm: vgic: Override the group in lr everytime

[Julien Grall <julien.grall@xxxxxxx>]

Hi Andre,

On 03/14/2018 06:02 PM, Andre Przywara wrote:
> On 09/03/18 17:35, julien.grall@xxxxxxx wrote:
> > From: Julien Grall <julien.grall@xxxxxxx>
> >
> > At the moment, write_lr is assuming the caller will set correctly the
> > group. However the group should always be 0 when the guest is using
> > vGICv2 and 1 for vGICv3. As the caller should not care about the group,
> > override it directly.
> I think that makes sense, mostly because this is what KVM does as well.
> And it's a good idea to do this in write_lr().
>
> I understand that this is effectively what I did in the new VGIC, but it
> would be good to double check that this is the right thing to do
> for the old VGIC as well. Did you test this on some GICv3 h/w or the
> model? Or do we always call update_lr() anyway?
I had a patch to remove update_lr and use write_lr. I exercised the code 
with it but didn't send it because of some nasty bug with the priority 
in write_lr and the old vGIC.
On the old vGIC write_lr is only used when in gic_update_one_lr(...) 
combine with read_lr before. In that context we don't care about the 
group, so overwriting it is fine and the right thing to do.
Cheers,

--
Julien Grall

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