net/mlx5e: SHAMPO, Drop info array

The info array is used to store a pointer to the
dma address of the header and to the frag page. However,
this array is not really required:
- The frag page can be calculated from the header index
  frag page index = header index / headers per page.
- The dma address can be calculated through a formula:
  dma page address + header offset.

This series gets rid of the info array and uses the above
formulas instead.

The current_page_index was used in conjunction with the info array to
store page fragment indices. This variable is dropped as well.

There was no performance regression observed.

Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20241107194357.683732-12-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

3 files changed, 42 insertions, 44 deletions

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en.h b/drivers/net/ethernet/mellanox/mlx5/core/en.h
index b4abb094f01a..979fc56205e1 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en.h
@@ -83,6 +83,7 @@ struct page_pool;
 #define MLX5E_SHAMPO_LOG_HEADER_ENTRY_SIZE (8)
 #define MLX5E_SHAMPO_LOG_MAX_HEADER_ENTRY_SIZE (9)
 #define MLX5E_SHAMPO_WQ_HEADER_PER_PAGE (PAGE_SIZE >> MLX5E_SHAMPO_LOG_MAX_HEADER_ENTRY_SIZE)
+#define MLX5E_SHAMPO_LOG_WQ_HEADER_PER_PAGE (PAGE_SHIFT - MLX5E_SHAMPO_LOG_MAX_HEADER_ENTRY_SIZE)
 #define MLX5E_SHAMPO_WQ_BASE_HEAD_ENTRY_SIZE (64)
 #define MLX5E_SHAMPO_WQ_RESRV_SIZE (64 * 1024)
 #define MLX5E_SHAMPO_WQ_BASE_RESRV_SIZE (4096)
@@ -624,9 +625,7 @@ struct mlx5e_dma_info {
 
 struct mlx5e_shampo_hd {
 	u32 mkey;
-	struct mlx5e_dma_info *info;
 	struct mlx5e_frag_page *pages;
-	u16 curr_page_index;
 	u32 hd_per_wq;
 	u16 hd_per_wqe;
 	u16 pages_per_wq;
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index 3ca1ef1f39a5..2e27e9d6b820 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -350,19 +350,15 @@ static int mlx5e_rq_shampo_hd_info_alloc(struct mlx5e_rq *rq, int node)
 
 	shampo->bitmap = bitmap_zalloc_node(shampo->hd_per_wq, GFP_KERNEL,
 					    node);
-	shampo->info = kvzalloc_node(array_size(shampo->hd_per_wq,
-						sizeof(*shampo->info)),
-				     GFP_KERNEL, node);
 	shampo->pages = kvzalloc_node(array_size(shampo->hd_per_wq,
 						 sizeof(*shampo->pages)),
 				     GFP_KERNEL, node);
-	if (!shampo->bitmap || !shampo->info || !shampo->pages)
+	if (!shampo->bitmap || !shampo->pages)
 		goto err_nomem;
 
 	return 0;
 
 err_nomem:
-	kvfree(shampo->info);
 	kvfree(shampo->bitmap);
 	kvfree(shampo->pages);
 
@@ -372,7 +368,6 @@ err_nomem:
 static void mlx5e_rq_shampo_hd_info_free(struct mlx5e_rq *rq)
 {
 	kvfree(rq->mpwqe.shampo->bitmap);
-	kvfree(rq->mpwqe.shampo->info);
 	kvfree(rq->mpwqe.shampo->pages);
 }
 
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
index 637069c1b988..3de575875586 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
@@ -643,6 +643,21 @@ static void build_ksm_umr(struct mlx5e_icosq *sq, struct mlx5e_umr_wqe *umr_wqe,
 	umr_wqe->uctrl.mkey_mask     = cpu_to_be64(MLX5_MKEY_MASK_FREE);
 }
 
+static struct mlx5e_frag_page *mlx5e_shampo_hd_to_frag_page(struct mlx5e_rq *rq, int header_index)
+{
+	BUILD_BUG_ON(MLX5E_SHAMPO_LOG_MAX_HEADER_ENTRY_SIZE > PAGE_SHIFT);
+
+	return &rq->mpwqe.shampo->pages[header_index >> MLX5E_SHAMPO_LOG_WQ_HEADER_PER_PAGE];
+}
+
+static u64 mlx5e_shampo_hd_offset(int header_index)
+{
+	return (header_index & (MLX5E_SHAMPO_WQ_HEADER_PER_PAGE - 1)) <<
+		MLX5E_SHAMPO_LOG_MAX_HEADER_ENTRY_SIZE;
+}
+
+static void mlx5e_free_rx_shampo_hd_entry(struct mlx5e_rq *rq, u16 header_index);
+
 static int mlx5e_build_shampo_hd_umr(struct mlx5e_rq *rq,
 				     struct mlx5e_icosq *sq,
 				     u16 ksm_entries, u16 index)
@@ -650,9 +665,6 @@ static int mlx5e_build_shampo_hd_umr(struct mlx5e_rq *rq,
 	struct mlx5e_shampo_hd *shampo = rq->mpwqe.shampo;
 	u16 pi, header_offset, err, wqe_bbs;
 	u32 lkey = rq->mdev->mlx5e_res.hw_objs.mkey;
-	u16 page_index = shampo->curr_page_index;
-	struct mlx5e_frag_page *frag_page = NULL;
-	struct mlx5e_dma_info *dma_info;
 	struct mlx5e_umr_wqe *umr_wqe;
 	int headroom, i;
 	u64 addr = 0;
@@ -665,29 +677,20 @@ static int mlx5e_build_shampo_hd_umr(struct mlx5e_rq *rq,
 
 	WARN_ON_ONCE(ksm_entries & (MLX5E_SHAMPO_WQ_HEADER_PER_PAGE - 1));
 	for (i = 0; i < ksm_entries; i++, index++) {
-		dma_info = &shampo->info[index];
-		header_offset = (index & (MLX5E_SHAMPO_WQ_HEADER_PER_PAGE - 1)) <<
-			MLX5E_SHAMPO_LOG_MAX_HEADER_ENTRY_SIZE;
-		if (!(header_offset & (PAGE_SIZE - 1))) {
-			frag_page = &shampo->pages[page_index];
-			page_index = (page_index + 1) & (shampo->pages_per_wq - 1);
+		header_offset = mlx5e_shampo_hd_offset(index);
+		if (!header_offset) {
+			struct mlx5e_frag_page *frag_page = mlx5e_shampo_hd_to_frag_page(rq, index);
 
 			err = mlx5e_page_alloc_fragmented(rq, frag_page);
 			if (unlikely(err))
 				goto err_unmap;
 
 			addr = page_pool_get_dma_addr(frag_page->page);
-
-			dma_info->addr = addr;
-			dma_info->frag_page = frag_page;
-		} else {
-			dma_info->addr = addr + header_offset;
-			dma_info->frag_page = frag_page;
 		}
 
 		umr_wqe->inline_ksms[i] = (struct mlx5_ksm) {
 			.key = cpu_to_be32(lkey),
-			.va  = cpu_to_be64(dma_info->addr + headroom),
+			.va  = cpu_to_be64(addr + header_offset + headroom),
 		};
 	}
 
@@ -698,20 +701,22 @@ static int mlx5e_build_shampo_hd_umr(struct mlx5e_rq *rq,
 	};
 
 	shampo->pi = (shampo->pi + ksm_entries) & (shampo->hd_per_wq - 1);
-	shampo->curr_page_index = page_index;
 	sq->pc += wqe_bbs;
 	sq->doorbell_cseg = &umr_wqe->ctrl;
 
 	return 0;
 
 err_unmap:
-	while (--i >= 0) {
-		dma_info = &shampo->info[--index];
-		if (!(i & (MLX5E_SHAMPO_WQ_HEADER_PER_PAGE - 1))) {
-			dma_info->addr = ALIGN_DOWN(dma_info->addr, PAGE_SIZE);
-			mlx5e_page_release_fragmented(rq, dma_info->frag_page);
+	while (--i) {
+		--index;
+		header_offset = mlx5e_shampo_hd_offset(index);
+		if (!header_offset) {
+			struct mlx5e_frag_page *frag_page = mlx5e_shampo_hd_to_frag_page(rq, index);
+
+			mlx5e_page_release_fragmented(rq, frag_page);
 		}
 	}
+
 	rq->stats->buff_alloc_err++;
 	return err;
 }
@@ -844,13 +849,11 @@ static void
 mlx5e_free_rx_shampo_hd_entry(struct mlx5e_rq *rq, u16 header_index)
 {
 	struct mlx5e_shampo_hd *shampo = rq->mpwqe.shampo;
-	u64 addr = shampo->info[header_index].addr;
 
 	if (((header_index + 1) & (MLX5E_SHAMPO_WQ_HEADER_PER_PAGE - 1)) == 0) {
-		struct mlx5e_dma_info *dma_info = &shampo->info[header_index];
+		struct mlx5e_frag_page *frag_page = mlx5e_shampo_hd_to_frag_page(rq, header_index);
 
-		dma_info->addr = ALIGN_DOWN(addr, PAGE_SIZE);
-		mlx5e_page_release_fragmented(rq, dma_info->frag_page);
+		mlx5e_page_release_fragmented(rq, frag_page);
 	}
 	clear_bit(header_index, shampo->bitmap);
 }
@@ -1204,10 +1207,10 @@ static void mlx5e_lro_update_hdr(struct sk_buff *skb, struct mlx5_cqe64 *cqe,
 
 static void *mlx5e_shampo_get_packet_hd(struct mlx5e_rq *rq, u16 header_index)
 {
-	struct mlx5e_dma_info *last_head = &rq->mpwqe.shampo->info[header_index];
-	u16 head_offset = (last_head->addr & (PAGE_SIZE - 1)) + rq->buff.headroom;
+	struct mlx5e_frag_page *frag_page = mlx5e_shampo_hd_to_frag_page(rq, header_index);
+	u16 head_offset = mlx5e_shampo_hd_offset(header_index) + rq->buff.headroom;
 
-	return page_address(last_head->frag_page->page) + head_offset;
+	return page_address(frag_page->page) + head_offset;
 }
 
 static void mlx5e_shampo_update_ipv4_udp_hdr(struct mlx5e_rq *rq, struct iphdr *ipv4)
@@ -2178,29 +2181,30 @@ static struct sk_buff *
 mlx5e_skb_from_cqe_shampo(struct mlx5e_rq *rq, struct mlx5e_mpw_info *wi,
 			  struct mlx5_cqe64 *cqe, u16 header_index)
 {
-	struct mlx5e_dma_info *head = &rq->mpwqe.shampo->info[header_index];
-	u16 head_offset = head->addr & (PAGE_SIZE - 1);
+	struct mlx5e_frag_page *frag_page = mlx5e_shampo_hd_to_frag_page(rq, header_index);
+	dma_addr_t page_dma_addr = page_pool_get_dma_addr(frag_page->page);
+	u16 head_offset = mlx5e_shampo_hd_offset(header_index);
+	dma_addr_t dma_addr = page_dma_addr + head_offset;
 	u16 head_size = cqe->shampo.header_size;
 	u16 rx_headroom = rq->buff.headroom;
 	struct sk_buff *skb = NULL;
 	void *hdr, *data;
 	u32 frag_size;
 
-	hdr		= page_address(head->frag_page->page) + head_offset;
+	hdr		= page_address(frag_page->page) + head_offset;
 	data		= hdr + rx_headroom;
 	frag_size	= MLX5_SKB_FRAG_SZ(rx_headroom + head_size);
 
 	if (likely(frag_size <= BIT(MLX5E_SHAMPO_LOG_MAX_HEADER_ENTRY_SIZE))) {
 		/* build SKB around header */
-		dma_sync_single_range_for_cpu(rq->pdev, head->addr, 0, frag_size, rq->buff.map_dir);
+		dma_sync_single_range_for_cpu(rq->pdev, dma_addr, 0, frag_size, rq->buff.map_dir);
 		net_prefetchw(hdr);
 		net_prefetch(data);
 		skb = mlx5e_build_linear_skb(rq, hdr, frag_size, rx_headroom, head_size, 0);
-
 		if (unlikely(!skb))
 			return NULL;
 
-		head->frag_page->frags++;
+		frag_page->frags++;
 	} else {
 		/* allocate SKB and copy header for large header */
 		rq->stats->gro_large_hds++;
@@ -2212,7 +2216,7 @@ mlx5e_skb_from_cqe_shampo(struct mlx5e_rq *rq, struct mlx5e_mpw_info *wi,
 		}
 
 		net_prefetchw(skb->data);
-		mlx5e_copy_skb_header(rq, skb, head->frag_page->page, head->addr,
+		mlx5e_copy_skb_header(rq, skb, frag_page->page, dma_addr,
 				      head_offset + rx_headroom,
 				      rx_headroom, head_size);
 		/* skb linear part was allocated with headlen and aligned to long */