[PATCH v2 4/4] vfio/pci: Allow MMIO regions to be exported through dma-buf

[Jason Gunthorpe]

On Tue, Sep 06, 2022 at 03:34:02PM +0300, Oded Gabbay wrote:

> > > > > + /*
> > > > > +  * Since the memory being mapped is a device memory it could never be in
> > > > > +  * CPU caches.
> > > > > +  */
> > > > DMA_ATTR_SKIP_CPU_SYNC doesn't even apply to dma_map_resource, not sure
> > > > where this wisdom comes from.
> >
> > Habana driver
> I hate to throw the ball at someone else, but I actually copied the
> code from the amdgpu driver, from amdgpu_vram_mgr_alloc_sgt() iirc.
> And if you remember Jason, you asked why we use this specific define
> in the original review you did and I replied the following (to which
> you agreed and that's why we added the comment):

Yes, I remember, but Christophs remark is that DMA_ATTR_SKIP_CPU_SYNC
doesn't even do anything when passed to dma_map_resource().

The only attr that seems to be used is DMA_ATTR_PRIVILEGED from what I
can see.

Jason