On Wed, Jan 21, 2026 at 10:20:51AM +0100, Christian König wrote:
On 1/20/26 15:07, Leon Romanovsky wrote:
From: Leon Romanovsky leonro@nvidia.com
dma-buf invalidation is performed asynchronously by hardware, so VFIO must wait until all affected objects have been fully invalidated.
Fixes: 5d74781ebc86 ("vfio/pci: Add dma-buf export support for MMIO regions") Signed-off-by: Leon Romanovsky leonro@nvidia.com
Reviewed-by: Christian König christian.koenig@amd.com
Please also keep in mind that the while this wait for all fences for correctness you also need to keep the mapping valid until dma_buf_unmap_attachment() was called.
Can you elaborate on this more?
I think what we want for dma_buf_attach_revocable() is the strong guarentee that the importer stops doing all access to the memory once this sequence is completed and the exporter can rely on it. I don't think this works any other way.
This is already true for dynamic move capable importers, right?
For the non-revocable importers I can see the invalidate sequence is more of an advisory thing and you can't know the access is gone until the map is undone.
In other words you can only redirect the DMA-addresses previously given out into nirvana (or a dummy memory or similar), but you still need to avoid re-using them for something else.
Does any driver do this? If you unload/reload a GPU driver it is going to re-use the addresses handed out?
Jason