[PATCH v8 1/5] RDMA/umem: Support importing dma-buf as user memory region

[Jason Gunthorpe]

On Fri, Nov 06, 2020 at 04:34:07PM +0000, Xiong, Jianxin wrote:

> > The user could specify a length that is beyond the dma buf, can
> > the dma buf length be checked during get?
> 
> In order to check the length, the buffer needs to be mapped. That can be done.

Do DMA bufs even have definitate immutable lengths? Going to be a
probelm if they can shrink

> > Also page_size can be 0 because iova is not OK. iova should be
> > checked for alignment during get as well:
> > 
> >   iova & (PAGE_SIZE-1) == umem->addr & (PAGE_SIZE-1)
> 
> If ib_umem_dmabuf_map_pages is called during get this error is automatically caught.

The ib_umem_find_best_pgsz() checks this equation, yes.

So you'd map the sgl before allocating the mkey? This then checks the
length and iova?

Jason