[PATCH v4] net/af_xdp: fix umem map size for zero copy

[Frank Du]

The current calculation assumes that the mbufs are contiguous. However,
this assumption is incorrect when the mbuf memory spans across huge page.
To ensure that each mbuf resides exclusively within a single page, there
are deliberate spacing gaps when allocating mbufs across the boundaries.

Correct to directly read the size from the mempool memory chunk.

Fixes: d8a210774e1d ("net/af_xdp: support unaligned umem chunks")
Cc: sta...@dpdk.org

Signed-off-by: Frank Du <frank...@intel.com>

---
v2:
* Add virtual contiguous detect for for multiple memhdrs
v3:
* Use RTE_ALIGN_FLOOR to get the aligned addr
* Add check on the first memhdr of memory chunks
v4:
* Replace the iterating with simple nb_mem_chunks check
---
 drivers/net/af_xdp/rte_eth_af_xdp.c | 33 +++++++++++++++++++++++------
 1 file changed, 26 insertions(+), 7 deletions(-)

diff --git a/drivers/net/af_xdp/rte_eth_af_xdp.c 
b/drivers/net/af_xdp/rte_eth_af_xdp.c
index 6ba455bb9b..d0431ec089 100644
--- a/drivers/net/af_xdp/rte_eth_af_xdp.c
+++ b/drivers/net/af_xdp/rte_eth_af_xdp.c
@@ -1040,16 +1040,32 @@ eth_link_update(struct rte_eth_dev *dev __rte_unused,
 }
 
 #if defined(XDP_UMEM_UNALIGNED_CHUNK_FLAG)
-static inline uintptr_t get_base_addr(struct rte_mempool *mp, uint64_t *align)
+static inline uintptr_t
+get_memhdr_info(const struct rte_mempool *mp, uint64_t *align, size_t *len)
 {
        struct rte_mempool_memhdr *memhdr;
        uintptr_t memhdr_addr, aligned_addr;
 
+       if (mp->nb_mem_chunks != 1) {
+               /*
+                * The mempool with multiple chunks is not virtual contiguous 
but
+                * xsk umem only support single virtual region mapping.
+                */
+               AF_XDP_LOG(ERR, "The mempool contain multiple %u memory 
chunks\n",
+                                  mp->nb_mem_chunks);
+               return 0;
+       }
+
+       /* Get the mempool base addr and align from the header now */
        memhdr = STAILQ_FIRST(&mp->mem_list);
+       if (!memhdr) {
+               AF_XDP_LOG(ERR, "The mempool is not populated\n");
+               return 0;
+       }
        memhdr_addr = (uintptr_t)memhdr->addr;
-       aligned_addr = memhdr_addr & ~(getpagesize() - 1);
+       aligned_addr = RTE_ALIGN_FLOOR(memhdr_addr, getpagesize());
        *align = memhdr_addr - aligned_addr;
-
+       *len = memhdr->len;
        return aligned_addr;
 }
 
@@ -1126,6 +1142,7 @@ xsk_umem_info *xdp_umem_configure(struct pmd_internals 
*internals,
        void *base_addr = NULL;
        struct rte_mempool *mb_pool = rxq->mb_pool;
        uint64_t umem_size, align = 0;
+       size_t len = 0;
 
        if (internals->shared_umem) {
                if (get_shared_umem(rxq, internals->if_name, &umem) < 0)
@@ -1157,10 +1174,12 @@ xsk_umem_info *xdp_umem_configure(struct pmd_internals 
*internals,
                }
 
                umem->mb_pool = mb_pool;
-               base_addr = (void *)get_base_addr(mb_pool, &align);
-               umem_size = (uint64_t)mb_pool->populated_size *
-                               (uint64_t)usr_config.frame_size +
-                               align;
+               base_addr = (void *)get_memhdr_info(mb_pool, &align, &len);
+               if (!base_addr) {
+                       AF_XDP_LOG(ERR, "The memory pool can't be mapped as 
umem\n");
+                       goto err;
+               }
+               umem_size = (uint64_t)len + align;
 
                ret = xsk_umem__create(&umem->umem, base_addr, umem_size,
                                &rxq->fq, &rxq->cq, &usr_config);
-- 
2.34.1