Re: [PATCH v2 1/2] iommu/virtio: Make use of ops->iotlb_sync_map

[Jason Gunthorpe]

On Fri, Sep 22, 2023 at 08:57:19AM +0100, Jean-Philippe Brucker wrote:
> > > They're not strictly equivalent: this check works around a temporary issue
> > > with the IOMMU core, which calls map/unmap before the domain is
> > > finalized.
> > 
> > Where? The above points to iommu_create_device_direct_mappings() but
> > it doesn't because the pgsize_bitmap == 0:
> 
> __iommu_domain_alloc() sets pgsize_bitmap in this case:
> 
>         /*
>          * If not already set, assume all sizes by default; the driver
>          * may override this later
>          */
>         if (!domain->pgsize_bitmap)
>                 domain->pgsize_bitmap = bus->iommu_ops->pgsize_bitmap;

Dirver's shouldn't do that.

The core code was fixed to try again with mapping reserved regions to
support these kinds of drivers.

Jason