Re: [PATCH for-4.15 v5 2/3] xen/x86: iommu: Ignore IOMMU mapping requests when a domain is dying

[Julien Grall <julien@xxxxxxx>]

Hi Jan,

On 26/02/2021 13:30, Jan Beulich wrote:
> On 26.02.2021 11:56, Julien Grall wrote:
> > From: Julien Grall <jgrall@xxxxxxxxxx>
> >
> > The new x86 IOMMU page-tables allocator will release the pages when
> > relinquishing the domain resources. However, this is not sufficient
> > when the domain is dying because nothing prevents page-table to be
> > allocated.
> >
> > As the domain is dying, it is not necessary to continue to modify the
> > IOMMU page-tables as they are going to be destroyed soon.
> >
> > At the moment, page-table allocates will only happen when iommu_map().
> > So after this change there will be no more page-table allocation
> > happening because we don't use superpage mappings yet when not sharing
> > page tables.
> >
> > In order to observe d->is_dying correctly, we need to rely on per-arch
> > locking, so the check to ignore IOMMU mapping is added on the per-driver
> > map_page() callback.
> >
> > Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
Thanks!

> Does this also want a Fixes: tag (the same as patch 1)?
I think so. I will add it when committing the series.

Cheers,

--
Julien Grall