On 7/23/2015 8:55 PM, Jason Gunthorpe wrote:
On Thu, Jul 23, 2015 at 01:15:16PM +0300, Sagi Grimberg wrote:
I was hoping we'd move the DMA flush and translate into here and make
it mandatory. Is there any reason not to do that?
The reason I didn't added it in was so the ULPs can make sure they meet
the restrictions of ib_map_mr_sg(). Allow SRP to iterate on his
SG list set partials and iSER to detect gaps (they need to dma map
for that).
The ULP can always get the sg list's virtual address to check for
gaps. Page aligned gaps are always OK.
I guess I can pull DMA mapping in there, but we will need an opposite
routine ib_umap_mr_sg() since it'll be weird if the ULP will do dma
unmap without doing the map...
BTW, the logic in ib_sg_to_pages should be checking that directly, as
coded, it won't work with swiotlb:
// Only the first SG entry can start unaligned
if (i && page_addr != dma_addr)
return EINVAL;
// Only the last SG entry can end unaligned
if ((page_addr + dma_len) & PAGE_MASK != end_dma_addr)
if (!is_last)
return EINVAL;
Don't use sg->offset after dma mapping.
The biggest problem with checking the virtual address is
swiotlb. However, if swiotlb is used this API is basically broken as
swiotlb downgrades everything to a 2k alignment, which means we only
ever get 1 s/g entry.
Can you explain what do you mean by "downgrades everything to a 2k
alignment"? If the ULP is responsible for a PAGE_SIZE alignment than
how would this get out of alignment with swiotlb?
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