On Tue, Apr 05, 2016 at 02:01:29PM -0700, Mitchel Humpherys wrote:
> Currently we use a single pgsize_bitmap per IOMMU driver. However, some
> IOMMU drivers might service different IOMMUs with different supported
> page sizes. Some drivers might also want to restrict page sizes for
> different use cases. Support these use cases by adding a
> .get_pgsize_bitmap function to the iommu_ops which can optionally be
> used by the driver to return a domain-specific pgsize_bitmap.
No, at least not this way. I said it before and I say it again: We are
not going to lift the iommu-api requirements in this undetectable way.
The iommu-api works with domains/groups and devices. The general
expectation is that every group can be part of every domain. I know that
this is not the case already with some drivers, but I am not going to
move the code further into the wrong direction.
The way I'd like to see that solved is:
* Introduce per-group pgsize-bitmaps (group->pgsize_bmp)
* Calculate a global pgsize-bitmap from all groups
pgsize-bitmaps
* Also store a pgsize_bitmap in each domain on allocation
* Modify iommu_domain_alloc to set domain->pgsize_bmp to the
global pgsize_bitmap
* Introduce an iommu_group_alloc_domain(group) function which
allocates a new domain only for the given group. This function
sets domain->pgsize_bitmap to group->pgsize_bmp.
* Note that now you can have multiple page-tables per domain,
one page-table for each required format.
Regards,
Joerg
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