From: Jason Gunthorpe jgg@nvidia.com
[ Upstream commit a40c20dabdf9045270767c75918feb67f0727c89 ]
It is possible for a single SGL to span an aligned boundary, eg if the SGL is
61440 -> 90112
Then the length is 28672, which currently limits the block size to 32k. With a 32k page size the two covering blocks will be:
32768->65536 and 65536->98304
However, the correct answer is a 128K block size which will span the whole 28672 bytes in a single block.
Instead of limiting based on length figure out which high IOVA bits don't change between the start and end addresses. That is the highest useful page size.
Fixes: 4a35339958f1 ("RDMA/umem: Add API to find best driver supported page size in an MR") Link: https://lore.kernel.org/r/1-v2-270386b7e60b+28f4-umem_1_jgg@nvidia.com Reviewed-by: Leon Romanovsky leonro@nvidia.com Reviewed-by: Shiraz Saleem shiraz.saleem@intel.com Signed-off-by: Jason Gunthorpe jgg@nvidia.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/infiniband/core/umem.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c index 0d42ba8c0b696..9be8f6c622db0 100644 --- a/drivers/infiniband/core/umem.c +++ b/drivers/infiniband/core/umem.c @@ -156,8 +156,13 @@ unsigned long ib_umem_find_best_pgsz(struct ib_umem *umem, return 0;
va = virt; - /* max page size not to exceed MR length */ - mask = roundup_pow_of_two(umem->length); + /* The best result is the smallest page size that results in the minimum + * number of required pages. Compute the largest page size that could + * work based on VA address bits that don't change. + */ + mask = pgsz_bitmap & + GENMASK(BITS_PER_LONG - 1, + bits_per((umem->length - 1 + virt) ^ virt)); /* offset into first SGL */ pgoff = umem->address & ~PAGE_MASK;