Re: [Xen-devel] [RFC 11/19] xen/passthrough: Call arch_iommu_domain_destroy before calling iommu_teardown

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi Ian,

On 17/06/14 09:07, Jan Beulich wrote:
> > > > On 16.06.14 at 18:17, <julien.grall@xxxxxxxxxx> wrote:
> > --- a/xen/drivers/passthrough/iommu.c
> > +++ b/xen/drivers/passthrough/iommu.c
> > @@ -219,10 +219,10 @@ void iommu_domain_destroy(struct domain *d)
> >       if ( !iommu_enabled || !hd->platform_ops )
> >           return;
> >
> > +    arch_iommu_domain_destroy(d);
> > +
> >       if ( need_iommu(d) )
> >           iommu_teardown(d);
> > -
> > -    arch_iommu_domain_destroy(d);
> At the first glance this doesn't look right, including the explanation
> you gave (why would devices still be assigned to a guest at this
> point).
Because the toolstack may forget to deassign a device. How do you handle 
this case in x86? In the SMMU case, this will mean a memory leak and 
misconfiguration of the registers.
I think it's safer to let Xen deassign the remaining devices.

> And it's rather hard to properly decide with the series here
> depending on two other series, i.e. there not being a
> arch_iommu_domain_destroy() at all in current staging.
Are you sure? The other series doesn't deal with the IOMMU stuff. This 
change has been pushed upstream a month ago (see commit 4905b35c " 
iommu: introduce arch specific code").
Regards,

--
Julien Grall

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