[PATCH v6 1/4] RDMA/umem: Support importing dma-buf as user memory region

[Jason Gunthorpe]

On Sat, Oct 24, 2020 at 08:48:07AM +0100, Christoph Hellwig wrote:
> On Fri, Oct 23, 2020 at 03:20:05PM -0300, Jason Gunthorpe wrote:
> > The problem is we have RDMA drivers that assume SGL's have a valid
> > struct page, and these hacky/wrong P2P sgls that DMABUF creates cannot
> > be passed into those drivers.
> 
> RDMA drivers do not assume scatterlist have a valid struct page,
> scatterlists are defined to have a valid struct page.  Any scatterlist
> without a struct page is completely buggy.

It is not just having the struct page, it needs to be a CPU accessible
one for memcpy/etc. They aren't correct with the
MEMORY_DEVICE_PCI_P2PDMA SGLs either.

Jason