Re: use exact allocation for dma coherent memory

Jason Gunthorpe
2019-06-19T16:29:03Z

On Mon, Jun 17, 2019 at 10:33:42AM +0200, Christoph Hellwig wrote:
> > drivers/infiniband/hw/cxgb4/qp.c
> > 129 static int alloc_host_sq(struct c4iw_rdev *rdev, struct t4_sq *sq)
> > 130 {
> > 131 sq->queue = dma_alloc_coherent(&(rdev->lldi.pdev->dev), sq->memsize,
> > 132 &(sq->dma_addr), GFP_KERNEL);
> > 133 if (!sq->queue)
> > 134 return -ENOMEM;
> > 135 sq->phys_addr = virt_to_phys(sq->queue);
> > 136 dma_unmap_addr_set(sq, mapping, sq->dma_addr);
> > 137 return 0;
> > 138 }
> >
> > Is this a bug?
>
> Yes. This will blow up badly on many platforms, as sq->queue
> might be vmapped, ioremapped, come from a pool without page backing.

Gah, this addr gets fed into io_remap_pfn_range/remap_pfn_range too..

Potnuri, you should fix this..

You probably need to use dma_mmap_from_dev_coherent() in the mmap ?

Jason