Am 02.08.2017 um 18:43 schrieb Jerome Glisse:
On Wed, Aug 02, 2017 at 10:26:40AM +0200, Christian König wrote:
[SNIP]
So to summarize you are saying you do not trust the value you get from
pci_map_page() ?
Well, what we don't trust is that we actually get this value correctly
into our page tables.
If not then i stress again that you have all the informations you need
inside the amdgpu driver. You can take the same scheme i propose to
dump ttm.dma_address[] and compare against content of GPU page table.
Yes, exactly. But then again we have the mapping page to dma-address
(because that is what drivers usually need), but what we need for
debugging is a map with the info dma-address to page.
I mean we can obviously build the reverse table in the driver ourself,
but that is just a waste of memory if you ask me cause the IOMMU driver
should have that info in it's tables anyway.
Additional to that we have at least some plans to get away from BOs and
towards HMM. So it would be nice to have a central debugging feature to
access the iommu map.
I'm actually surprised that the IOMMU subsystem doesn't already have
something like that somewhere. I mean how do you guys validate that
what's written into the IOMMU tables is actually correct?
Isn't there some way (debugfs/sysfs/tools?) to dump them?
Regards,
Christian.
Jérôme
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