On 21/01/2021 11:03, Chris Wilson wrote:
Quoting Tvrtko Ursulin (2021-01-21 11:00:25)
On 20/01/2021 20:59, Chris Wilson wrote:
Quoting Chris Wilson (2021-01-20 18:06:08)
Quoting Matthew Auld (2021-01-20 17:46:10)
On Wed, 20 Jan 2021 at 15:40, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote:
If we import a shmemfs object between devices, for example from
Tigerlake to DG1, we can simply reuse the native object and its backing
store.
Hmmm interesting, so does that include re-using the actual sg mapping
for the backing pages? Does that work out-of-the-box between different
devices assuming we have iommu enabled?
Indeed interesting; the dma_addr_t are supposed to be local to a device.
On reflection, we are expected to use cross-device dma_addr_t with
dma-buf. It's the exporter who assigns the dma_addr_t for the importer
to use, and they are always given from the original device.
Maybe not so bad. Definitely needs testing to see what happens in
practice.
What about object migration? I did not spot anything preventing it once
object was exported like this so owning device could move it to device
memory afterwards which would probably be bad.
Depends on how you do your migration, but your migration should be
checking that it is allowed to migrate the object first.
Okay agreed, meaning to be handled once migration gets to upstream.
Regards,
Tvrtko
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