Re: [Xen-devel] [PATCH v4.1 4/6] xen/x86: Allow stubdom access to irq created for msi.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 27.02.19 at 16:18, <marmarek@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> On Wed, Feb 27, 2019 at 04:07:54AM -0700, Jan Beulich wrote:
>> >>> On 08.02.19 at 11:17, <marmarek@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>> > @@ -190,19 +190,19 @@ int create_irq(nodeid_t node)
>> >          desc->arch.used = IRQ_UNUSED;
>> >          irq = ret;
>> >      }
>> > -    else if ( hardware_domain )
>> > +    else if ( dm_domain )
>> >      {
>> > -        ret = irq_permit_access(hardware_domain, irq);
>> > +        ret = irq_permit_access(dm_domain, irq);
>> 
>> Doesn't this imply that Dom0 has no way of cleaning up after the
>> guest/stubdom pair? IOW I wonder whether both dm and hwdom
>> should be granted access.
> 
> See discussion with Roger on this very patch.
> In short: since permissions are stored in domain struct, not irq, there
> is not much to cleanup after domain destruction.

My point wasn't about cleaning up permissions, but about cleaning
up the IRQs. Dom0 can't do anything with them without being
given permission.

> Also, toolstack in dom0
> has no idea about IRQs allocated by stubdomain, so it couldn't do such
> cleanup anyway.

Well, a last resort cleanup could always be to iterate over all possible
IRQs. Whether that's helpful on top of Xen internal cleanup depends
on how much we care about cleaning up resources of zombie domains
as much as possible.

Jan



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