[Linaro-mm-sig] Re: [RFC v2 PATCH 09/10] vfio/pci: Add mmap() attributes to DMABUF feature

HI Jason,

On Mon, Mar 30, 2026 at 2:33 PM Jason Gunthorpe jgg@nvidia.com wrote:

On Thu, Mar 12, 2026 at 11:46:07AM -0700, Matt Evans wrote:

...

A new field is reserved in vfio_device_feature_dma_buf.flags to request CPU-facing memory type attributes for mmap()s of the buffer. Add a flag VFIO_DEVICE_FEATURE_DMA_BUF_ATTR_WC, which results in WC PTEs for the DMABUF's BAR region.

This seems very straightforward, I like it

Did I get it right that the idea is the user would request a dmabuf with these flags and then mmap the dmabuf?

Right, export it with a requested attribute (as possibly some sub-slice(s) of a larger BAR if you like) and then map it (no attributes need to be specified at mmap() time).

Thanks,

Matt