On Thu, Oct 16, 2025 at 11:33:52PM -0700, Christoph Hellwig wrote:
On Mon, Oct 13, 2025 at 06:26:11PM +0300, Leon Romanovsky wrote:
From: Leon Romanovsky leonro@nvidia.com
Add support for exporting PCI device MMIO regions through dma-buf, enabling safe sharing of non-struct page memory with controlled lifetime management. This allows RDMA and other subsystems to import dma-buf FDs and build them into memory regions for PCI P2P operations.
The implementation provides a revocable attachment mechanism using dma-buf move operations. MMIO regions are normally pinned as BARs don't change physical addresses, but access is revoked when the VFIO device is closed or a PCI reset is issued. This ensures kernel self-defense against potentially hostile userspace.
This still completely fails to explain why you think that it actually is safe without the proper pgmap handling.
Leon, this keeps coming up, please clean up and copy the text from my prior email into the commit message & cover letter explaining in detail how lifetime magement works by using revocation/invalidation driven by dmabuf move_notify callbacks.
Jason