On 22/09/2023 1:41 pm, Jason Gunthorpe wrote:
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.
This is still the "normal" code path, really; I think it's only AMD that
started initialising the domain bitmap "early" and warranted making it
conditional. However we *do* ultimately want all the drivers to do the
same, so we can get rid of ops->pgsize_bitmap, because it's already
pretty redundant and meaningless in the face of per-domain pagetable
formats.
Thanks,
Robin.
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