Re: [Xen-devel] [PATCH v5 4/6] xen/x86: Allow stubdom access to irq created for msi.

[Julien Grall <julien.grall@xxxxxxx>]

On 22/07/2019 10:06, Julien Grall wrote:
> Hi Roger,
>
> On 22/07/2019 09:45, Roger Pau Monné wrote:
> > On Sun, Jul 21, 2019 at 07:05:16PM +0100, Julien Grall wrote:
> > > Hi,
> > >
> > > On 7/20/19 10:21 PM, Marek Marczykowski-Górecki wrote:
> > > > On Sat, Jul 20, 2019 at 05:48:56PM +0100, Julien Grall wrote:
> > > > > Hi,
> > > > >
> > > > > Sorry for jumping late in the discussion.
> > > > >
> > > > > On 7/17/19 2:00 AM, Marek Marczykowski-Górecki wrote:
> > > > > > diff --git a/xen/include/xen/irq.h b/xen/include/xen/irq.h
> > > > > > index 586b783..c7a6a83 100644
> > > > > > --- a/xen/include/xen/irq.h
> > > > > > +++ b/xen/include/xen/irq.h
> > > > > > @@ -91,6 +91,7 @@ typedef struct irq_desc {
> > > > > >         spinlock_t lock;
> > > > > >         struct arch_irq_desc arch;
> > > > > >         cpumask_var_t affinity;
> > > > > > +    domid_t creator_domid; /* weak reference to domain handling this IRQ */
> > > > > This x86 only. Can this be moved in arch_irq_desc to avoid increasing the
> > > > > structure on Arm?
> > > > How (if at all) PCI passthrough is supported on ARM? Is qemu involved?
> > > > If so, and if that qemu would be isolated in stubdomain, I think ARM
> > > > would need a similar feature. If it not the case right now, but it is
> > > > planned, do you think it's worth moving it to arch_irq_desc and possibly
> > > > move back later?
> > > PCI passthrough is not yet supported on Arm. However, I would not expect
> > > QEMU to be involved at all for Arm.
> > >
> > > In any case, I would still prefer to keep field in arch_irq_desc until we
> > > see any usage on Arm.
> > I'm fine with putting it inside of the arch struct, but there's
> > nothing x86 specific about this field.
> In theory yes, in practice this is only used by x86 today. I don't want to 
> increase the size of irq_desc for unused field.
> We can move because the field in irq_desc if there are a need on Arm.
s/because/later/


Cheers,

--
Julien Grall

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