On 30/07/2019 07:28, Christoph Hellwig wrote:
On Mon, Jul 29, 2019 at 04:32:38PM +0100, Robin Murphy wrote:
MSI pages must always be mapped into a device's *current* domain, which
*might* be the default DMA domain, but might instead be a VFIO domain
with its own MSI cookie. This subtlety got accidentally lost in the
streamlining of __iommu_dma_map(), but rather than reintroduce more
complexity and/or special-casing, it turns out neater to just split this
path out entirely.
Since iommu_dma_get_msi_page() already duplicates much of what
__iommu_dma_map() does, it can easily just make the allocation and
mapping calls directly as well. That way we can further streamline the
helper back to exclusively operating on DMA domains.
Fixes: b61d271e59d7 ("iommu/dma: Move domain lookup into
__iommu_dma_{map,unmap}")
Reported-by: Shameer Kolothum <shameerali.kolothum.th...@huawei.com>
Reported-by: Andre Przywara <andre.przyw...@arm.com>
Signed-off-by: Robin Murphy <robin.mur...@arm.com>
Hmm. I remember proposing this patch and you didn't like it because
we could also have msis for a !IOMMU_DMA_IOVA_COOKIE cookie type.
Or did we talk past each other?
Do you have a pointer? That sparks the vaguest of memories, but I can't
seem to turn anything up in my inbox. If that was my objection, though,
it sounds like your patch was probably trying to go a step or two
further than this one.
Note that if this change turns out to be valid we should also
clean up the iommu_dma_free_iova() side.
We're not touching the iommu_dma_{alloc,free}_iova() path here; those
are designed to cope with both types of cookie, and I think that's a
reasonable abstraction to keep. This is just getting rid of the
asymmetry - and now bug - caused by trying to keep the MSI page flow
going through a special case in __iommu_dma_map() despite that having
evolved into a more specific DMA domain fastpath (there's no
corresponding unmap special case since MSI mappings just persist and get
recycled until the domain is destroyed).
Robin.
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