From 4a35339958f16d42a4ca06a8da9d4b5ab39ee8ea Mon Sep 17 00:00:00 2001 From: Shiraz Saleem Date: Mon, 6 May 2019 08:53:32 -0500 Subject: RDMA/umem: Add API to find best driver supported page size in an MR This helper iterates through the SG list to find the best page size to use from a bitmap of HW supported page sizes. Drivers that support multiple page sizes, but not mixed sizes in an MR can use this API. Suggested-by: Jason Gunthorpe Signed-off-by: Shiraz Saleem Signed-off-by: Jason Gunthorpe --- drivers/infiniband/core/umem.c | 51 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 51 insertions(+) (limited to 'drivers/infiniband/core') diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c index 23f7512cc7a8..145c31c530ae 100644 --- a/drivers/infiniband/core/umem.c +++ b/drivers/infiniband/core/umem.c @@ -130,6 +130,57 @@ static struct scatterlist *ib_umem_add_sg_table(struct scatterlist *sg, return sg; } +/** + * ib_umem_find_best_pgsz - Find best HW page size to use for this MR + * + * @umem: umem struct + * @pgsz_bitmap: bitmap of HW supported page sizes + * @virt: IOVA + * + * This helper is intended for HW that support multiple page + * sizes but can do only a single page size in an MR. + * + * Returns 0 if the umem requires page sizes not supported by + * the driver to be mapped. Drivers always supporting PAGE_SIZE + * or smaller will never see a 0 result. + */ +unsigned long ib_umem_find_best_pgsz(struct ib_umem *umem, + unsigned long pgsz_bitmap, + unsigned long virt) +{ + struct scatterlist *sg; + unsigned int best_pg_bit; + unsigned long va, pgoff; + dma_addr_t mask; + int i; + + /* At minimum, drivers must support PAGE_SIZE or smaller */ + if (WARN_ON(!(pgsz_bitmap & GENMASK(PAGE_SHIFT, 0)))) + return 0; + + va = virt; + /* max page size not to exceed MR length */ + mask = roundup_pow_of_two(umem->length); + /* offset into first SGL */ + pgoff = umem->address & ~PAGE_MASK; + + for_each_sg(umem->sg_head.sgl, sg, umem->nmap, i) { + /* Walk SGL and reduce max page size if VA/PA bits differ + * for any address. + */ + mask |= (sg_dma_address(sg) + pgoff) ^ va; + if (i && i != (umem->nmap - 1)) + /* restrict by length as well for interior SGEs */ + mask |= sg_dma_len(sg); + va += sg_dma_len(sg) - pgoff; + pgoff = 0; + } + best_pg_bit = rdma_find_pg_bit(mask, pgsz_bitmap); + + return BIT_ULL(best_pg_bit); +} +EXPORT_SYMBOL(ib_umem_find_best_pgsz); + /** * ib_umem_get - Pin and DMA map userspace memory. * -- cgit v1.2.3