On Wed, Feb 12, 2020 at 02:09:03PM -0500, Chuck Lever wrote:
>
>
> > On Feb 12, 2020, at 2:05 PM, Jason Gunthorpe <jgg@xxxxxxxx> wrote:
> >
> > On Wed, Feb 12, 2020 at 01:38:59PM -0500, Chuck Lever wrote:
> >>
> >>> 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")
> >
> > Not really, this was broken for other configurations besides AMD
>
> Agreed, but the bug seems to have been inconsequential until now?
I imagine it would get you on ARM or other archs, IIRC.
Jason
