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

Robin Murphy
2022-11-29T18:41:34Z

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.