Re: [PATCH v2 4/7] iommu: Let iommu.strict override ops->def_domain_type

[Robin Murphy]

On 2022-11-29 17:33, Jason Gunthorpe wrote:
> On Mon, Nov 28, 2022 at 09:01:43PM +0000, Robin Murphy wrote:
>
> > I'm hardly an advocate for trying to save users from themselves, but I
> > honestly can't see any justifiable reason for not having sysfs respect
> > iommu_get_def_domain_type().
>
> We really need to rename this value if it is not actually just an
> advisory "default" but a functional requirement ..

It represents a required default domain type. As in, the type for the 
device's default domain. Not the default type for a domain. It's the 
iommu_def_domain_type variable that holds the *default* default domain 
type ;)

Which reminds me I should finish that patch undoing my terrible 
ops->default_domain_ops idea, not least because they are misleadingly 
unrelated to default domains...

> > > The driver should have no say in how dma-iommu.c works beyond if it
> > > provides the required ops functionalities, and hint(s) as to what
> > > gives best performance.
> >
> > That should already be the case today, as outlined in my other mail. It's
> > just somewhat more evolved than designed, so may not be so clear to
> > everyone.
>
> It is close to being clear, once we get the last touches of dma-iommu
> stuff out of the drivers it should be quite clear

Cool, some upheaval of .domain_alloc is next on my hitlist anyway, so 
that might be a good excuse to upheave it a bit more and streamline the 
type stuff along the way.

Cheers,
Robin.