Re: [Xen-devel] [PATCH 6/7] xen: Allow hardare domain != dom0

[Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>]

On 04/14/2014 03:56 AM, Jan Beulich wrote:
> > > > On 11.04.14 at 20:22, <dgdegra@xxxxxxxxxxxxx> wrote:
> > On 04/11/2014 11:20 AM, Jan Beulich wrote:
> > > > > > On 11.04.14 at 17:07, <dgdegra@xxxxxxxxxxxxx> wrote:
> > > > On 04/11/2014 05:13 AM, Jan Beulich wrote:
> > > > Otherwise, I think the is_hardware_domain definition should be:
> > > >
> > > > #ifdef CONFIG_LATE_HWDOM
> > > > #define is_hardware_domain(_d) ((_d)->domain_id == hardware_domid)
> > > > #else
> > > > #define is_hardware_domain(_d) ((_d)->domain_id == 0)
> > > > #endif
> > > >
> > > > This also allows hardware_domid to be declared inside the #ifdef.
> > > But that still wouldn't necessarily do the correct thing for any use of
> > > the macro before that new special case code in domain_create() got
> > > run. Maybe my thinking of this is wrong, but as I tried to state above,
> > > I would expect Dom0 to be the hardware domain up to the point
> > > where the intended hardware domain gets created, at which point all
> > > state Dom0 obtained because of having been the de-facto hardware
> > > domain get transferred to hardware_domain.
> > I agree with this in most cases, and I think the few places where that
> > is not true should be changed to make them more explicit.  This must
> > include all checks in domain_create and those in functions called from
> > domain_create, because (d == hardware_domain) is always false inside
> > domain_create.  An initial version of this patch is below, but unless
> > there are objections I plan to integrate it into patch 1 to avoid doing
> > (d->domain_id == 0) => is_hardware_domain => is_hardware_domain_by_id
> > for the ARM code.
> Integration into any earlier patch would work only if we reverted
> what was already applied.
Ah, I didn't see that part of the series was applied.  Anyway, I didn't
really like how far the full version (larger than the RFC below) ended up
having to propagate the _by_id version, so a different solution would be
better.

> > ------------------------------>8------------------------
> >
> > Subject: [PATCH RFC 6/8] xen: introduce is_hardware_domain_by_id
> Certainly not very nice a name, and also not very nice to then have
> two ways to check, which likely people will not always distinguish
> properly. I think this needs some better idea, albeit I can't immediately
> offer one.
>
> Jan
If the assignment to hardware_domain is moved into domain_create, this
makes the (d == hardware_domain) version of is_hardware_domain work as
expected, and removes the need for is_hardware_domain_by_id.  This also
makes the initialization look a bit cleaner; the patch will be posted
momentarily.

--
Daniel De Graaf
National Security Agency

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