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 <jgg@ziepe.ca>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c
index 23f7512cc7a80ea6f349981045f93c4c1ff3698b..145c31c530ae26fe5e4533680597ae4e95fceb5f 100644 (file)
--- 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.
  *

diff --git a/include/rdma/ib_umem.h b/include/rdma/ib_umem.h
index b13a2e9a50d4738337a98fb4cbb9901d756ad263..917b687010f0108922037d2b477a9e7c9b7a2ffc 100644 (file)
--- a/include/rdma/ib_umem.h
+++ b/include/rdma/ib_umem.h
@@ -87,6 +87,9 @@ void ib_umem_release(struct ib_umem *umem);
 int ib_umem_page_count(struct ib_umem *umem);
 int ib_umem_copy_from(void *dst, struct ib_umem *umem, size_t offset,
                      size_t length);
+unsigned long ib_umem_find_best_pgsz(struct ib_umem *umem,
+                                    unsigned long pgsz_bitmap,
+                                    unsigned long virt);
 
 #else /* CONFIG_INFINIBAND_USER_MEM */
 
@@ -104,6 +107,12 @@ static inline int ib_umem_copy_from(void *dst, struct ib_umem *umem, size_t offs
                                    size_t length) {
        return -EINVAL;
 }
+static inline int ib_umem_find_best_pgsz(struct ib_umem *umem,
+                                        unsigned long pgsz_bitmap,
+                                        unsigned long virt) {
+       return -EINVAL;
+}
+
 #endif /* CONFIG_INFINIBAND_USER_MEM */
 
 #endif /* IB_UMEM_H */

diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index 8f8965f8ffdb4938068f8cd88ae0a5602fbacc0e..03b07ec6a34b19584d0e1c290ee57f297f313d9e 100644 (file)
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -3250,6 +3250,30 @@ static inline bool rdma_cap_read_inv(struct ib_device *dev, u32 port_num)
        return rdma_protocol_iwarp(dev, port_num);
 }
 
+/**
+ * rdma_find_pg_bit - Find page bit given address and HW supported page sizes
+ *
+ * @addr: address
+ * @pgsz_bitmap: bitmap of HW supported page sizes
+ */
+static inline unsigned int rdma_find_pg_bit(unsigned long addr,
+                                           unsigned long pgsz_bitmap)
+{
+       unsigned long align;
+       unsigned long pgsz;
+
+       align = addr & -addr;
+
+       /* Find page bit such that addr is aligned to the highest supported
+        * HW page size
+        */
+       pgsz = pgsz_bitmap & ~(-align << 1);
+       if (!pgsz)
+               return __ffs(pgsz_bitmap);
+
+       return __fls(pgsz);
+}
+
 int ib_set_vf_link_state(struct ib_device *device, int vf, u8 port,
                         int state);
 int ib_get_vf_config(struct ib_device *device, int vf, u8 port,