Re: [PATCH V5 1/3] xen/arm: Introduce gpaddr_bits field to struct xen_arch_domainconfig

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Fri, 8 Oct 2021, Oleksandr wrote:
> On 08.10.21 15:36, Jan Beulich wrote:
> > On 08.10.2021 12:25, Oleksandr wrote:
> > > Just a quick question. What do you think can XEN_DOMCTL_getdomaininfo be
> > > reused to retrieve gpaddr_bits? I don't see why not at the moment, but
> > > maybe there are some implications/concerns which are invisible to me.
> > > 
> > > I see that arch_get_domain_info() is present, so the field will be
> > > common, and each arch will write a value it considers
> > > appropriate. This could be a good compromise to not add an extra domctl
> > > and to not alter domain_create.
> > Technically I think it could be reused. What I'm less certain of is
> > whether the specific piece of information is a good fit there.
> 
> ok, thank you for your answer.
> 
> I am also not 100% sure whether it is a *good* fit there, but I cannot say it
> is not fit at all for being there. I might mistake, but it is almost the same
> piece of information describing the whole domain as other existing fields in
> that structure.

>From a domctl point of view, it looks like XEN_DOMCTL_getdomaininfo
could be a decent fit. Looking at the data structure, the arch specific
member of struct xen_domctl_getdomaininfo is:

  struct xen_arch_domainconfig arch_config;

which is actually the very same struct used in struct
xen_domctl_createdomain for XEN_DOMCTL_createdomain, but somehow it
doesn't get populated by neither the x86 nor the ARM version of
arch_get_domain_info?


In any case, I think we could make use of XEN_DOMCTL_getdomaininfo for
this. In that case, I would add a new common field to struct
xen_domctl_getdomaininfo after cpupool and above arch_config.

Then we can set the field from arch_get_domain_info.