> On Feb 12, 2020, at 1:26 PM, Jason Gunthorpe <jgg@xxxxxxxx> wrote:
>
> On Wed, Feb 12, 2020 at 11:12:30AM -0500, Chuck Lever wrote:
>> The @nents value that was passed to ib_dma_map_sg() has to be passed
>> to the matching ib_dma_unmap_sg() call. If ib_dma_map_sg() choses to
>> concatenate sg entries, it will return a different nents value than
>> it was passed.
>>
>> The bug was exposed by recent changes to the AMD IOMMU driver, which
>> enabled sg entry concatenation.
>>
>> Looking all the way back to commit 4143f34e01e9 ("xprtrdma: Port to
>> new memory registration API") and reviewing other kernel ULPs, it's
>> not clear that the frwr_map() logic was ever correct for this case.
>>
>> Reported-by: Andre Tomt <andre@xxxxxxxx>
>> Suggested-by: Robin Murphy <robin.murphy@xxxxxxx>
>> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
>> Cc: stable@xxxxxxxxxxxxxxx # v5.5
>> ---
>> net/sunrpc/xprtrdma/frwr_ops.c | 13 +++++++------
>> 1 file changed, 7 insertions(+), 6 deletions(-)
>
> Yep
>
> Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Thanks.
Wondering if it makes sense to add a Fixes tag for the AMD IOMMU commit
where NFS/RDMA stopped working, rather than the "Cc: stable # v5.5".
Fixes: be62dbf554c5 ("iommu/amd: Convert AMD iommu driver to the dma-iommu api")
--
Chuck Lever
