Re: [Xen-devel] [v3 12/13] arm: Allow the user to specify the GIC version

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Julien Grall writes ("[v3 12/13] arm: Allow the user to specify the GIC 
version"):
> A platform may have a GIC compatible with previous version of the
> device.
...
> +=item B<gic_version="vN">
> +
> +Version of the GIC emulated for the guest. Currently, the following
> +versions are supported:

This documentation should say what happens if this is not specified.

If the default behaviour is not simply `v3' (which I think it isn't)
then there should be a way to explicitly request it.  That is, there
should not be a behaviour which is only obtainable by not setting the
config option.  Instead, there should be a config option value to
request whatever that behaviour is.  (At the xl layer.)

AFIACT the default is "offer the guest the hardware's native version".
I think having called this XEN_DOMCTL_CONFIG_GIC_DEFAULT is rather
odd.  I think "native" would be a better description.

It might be better to deal with this default-filling-in by changing
the value in the domain config struct along with the other setdefault
type things in libxl_create.c.  If you do that, then saying
`libxl_domain_create_new', and then looking at the supplied config,
will give you a config specifying the GIC version explicitly, which I
think is more correct.

Ian.

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