net/mlx5e: RX, Remove alloc unit layout constraint for legacy rq

The mlx5e_alloc_unit union is conveniently used to store arrays of
pointers to struct page or struct xdp_buff (for xsk). The union is
currently expected to have the size of a pointer for xsk batch
allocations to work. This is conveniet for the current state of the
code but makes it impossible to add a structure of a different size
to the alloc unit.

A further patch in the series will add the mlx5e_frag_page struct for
which the described size constraint will no longer hold.

This change removes the usage of mlx5e_alloc_unit union for legacy rq:

- A union of arrays is introduced (mlx5e_alloc_units) to replace the
  array of unions to allow structures of different sizes.

- Each fragment has a pointer to a unit in the mlx5e_alloc_units array.
Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

drivers/net/ethernet/mellanox/mlx5/core/en.h

@@ -606,11 +606,19 @@ struct mlx5e_icosq {
 } ____cacheline_aligned_in_smp;
 
 struct mlx5e_wqe_frag_info {
-	union mlx5e_alloc_unit *au;
+	union {
+		struct page **pagep;
+		struct xdp_buff **xskp;
+	};
 	u32 offset;
 	bool last_in_page;
 };
 
+union mlx5e_alloc_units {
+	DECLARE_FLEX_ARRAY(struct page *, pages);
+	DECLARE_FLEX_ARRAY(struct xdp_buff *, xsk_buffs);
+};
+
 struct mlx5e_mpw_info {
 	u16 consumed_strides;
 	DECLARE_BITMAP(xdp_xmit_bitmap, MLX5_MPWRQ_MAX_PAGES_PER_WQE);
@@ -702,7 +710,7 @@ struct mlx5e_rq {
 		struct {
 			struct mlx5_wq_cyc          wq;
 			struct mlx5e_wqe_frag_info *frags;
-			union mlx5e_alloc_unit     *alloc_units;
+			union mlx5e_alloc_units    *alloc_units;
 			struct mlx5e_rq_frags_info  info;
 			mlx5e_fp_skb_from_cqe       skb_from_cqe;
 		} wqe;

drivers/net/ethernet/mellanox/mlx5/core/en/xsk/rx.c

@@ -163,13 +163,10 @@ int mlx5e_xsk_alloc_rx_wqes_batched(struct mlx5e_rq *rq, u16 ix, int wqe_bulk)
 	u32 contig, alloc;
 	int i;
 
-	/* mlx5e_init_frags_partition creates a 1:1 mapping between
-	 * rq->wqe.frags and rq->wqe.alloc_units, which allows us to
-	 * allocate XDP buffers straight into alloc_units.
+	/* Each rq->wqe.frags->xskp is 1:1 mapped to an element inside the
+	 * rq->wqe.alloc_units->xsk_buffs array allocated here.
 	 */
-	BUILD_BUG_ON(sizeof(rq->wqe.alloc_units[0]) !=
-		     sizeof(rq->wqe.alloc_units[0].xsk));
-	buffs = (struct xdp_buff **)rq->wqe.alloc_units;
+	buffs = rq->wqe.alloc_units->xsk_buffs;
 	contig = mlx5_wq_cyc_get_size(wq) - ix;
 	if (wqe_bulk <= contig) {
 		alloc = xsk_buff_alloc_batch(rq->xsk_pool, buffs + ix, wqe_bulk);
@@ -189,7 +186,7 @@ int mlx5e_xsk_alloc_rx_wqes_batched(struct mlx5e_rq *rq, u16 ix, int wqe_bulk)
 		/* Assumes log_num_frags == 0. */
 		frag = &rq->wqe.frags[j];
 
-		addr = xsk_buff_xdp_get_frame_dma(frag->au->xsk);
+		addr = xsk_buff_xdp_get_frame_dma(*frag->xskp);
 		wqe->data[0].addr = cpu_to_be64(addr + rq->buff.headroom);
 	}
 
@@ -211,11 +208,11 @@ int mlx5e_xsk_alloc_rx_wqes(struct mlx5e_rq *rq, u16 ix, int wqe_bulk)
 		/* Assumes log_num_frags == 0. */
 		frag = &rq->wqe.frags[j];
 
-		frag->au->xsk = xsk_buff_alloc(rq->xsk_pool);
-		if (unlikely(!frag->au->xsk))
+		*frag->xskp = xsk_buff_alloc(rq->xsk_pool);
+		if (unlikely(!*frag->xskp))
 			return i;
 
-		addr = xsk_buff_xdp_get_frame_dma(frag->au->xsk);
+		addr = xsk_buff_xdp_get_frame_dma(*frag->xskp);
 		wqe->data[0].addr = cpu_to_be64(addr + rq->buff.headroom);
 	}
 
@@ -306,7 +303,7 @@ struct sk_buff *mlx5e_xsk_skb_from_cqe_linear(struct mlx5e_rq *rq,
 					      struct mlx5_cqe64 *cqe,
 					      u32 cqe_bcnt)
 {
-	struct mlx5e_xdp_buff *mxbuf = xsk_buff_to_mxbuf(wi->au->xsk);
+	struct mlx5e_xdp_buff *mxbuf = xsk_buff_to_mxbuf(*wi->xskp);
 	struct bpf_prog *prog;
 
 	/* wi->offset is not used in this function, because xdp->data and the

drivers/net/ethernet/mellanox/mlx5/core/en_main.c

@@ -499,15 +499,9 @@ static void mlx5e_init_frags_partition(struct mlx5e_rq *rq)
 	struct mlx5e_wqe_frag_info *prev = NULL;
 	int i;
 
-	if (rq->xsk_pool) {
-		/* Assumptions used by XSK batched allocator. */
-		WARN_ON(rq->wqe.info.num_frags != 1);
-		WARN_ON(rq->wqe.info.log_num_frags != 0);
-		WARN_ON(rq->wqe.info.arr[0].frag_stride != PAGE_SIZE);
-	}
-
-	next_frag.au = &rq->wqe.alloc_units[0];
+	WARN_ON(rq->xsk_pool);
 
+	next_frag.pagep = &rq->wqe.alloc_units->pages[0];
 	for (i = 0; i < mlx5_wq_cyc_get_size(&rq->wqe.wq); i++) {
 		struct mlx5e_rq_frag_info *frag_info = &rq->wqe.info.arr[0];
 		struct mlx5e_wqe_frag_info *frag =
@@ -516,7 +510,8 @@ static void mlx5e_init_frags_partition(struct mlx5e_rq *rq)
 
 		for (f = 0; f < rq->wqe.info.num_frags; f++, frag++) {
 			if (next_frag.offset + frag_info[f].frag_stride > PAGE_SIZE) {
-				next_frag.au++;
+				/* Pages are assigned at runtime. */
+				next_frag.pagep++;
 				next_frag.offset = 0;
 				if (prev)
 					prev->last_in_page = true;
@@ -533,22 +528,59 @@ static void mlx5e_init_frags_partition(struct mlx5e_rq *rq)
 		prev->last_in_page = true;
 }
 
-static int mlx5e_init_au_list(struct mlx5e_rq *rq, int wq_sz, int node)
+static void mlx5e_init_xsk_buffs(struct mlx5e_rq *rq)
+{
+	int i;
+
+	/* Assumptions used by XSK batched allocator. */
+	WARN_ON(rq->wqe.info.num_frags != 1);
+	WARN_ON(rq->wqe.info.log_num_frags != 0);
+	WARN_ON(rq->wqe.info.arr[0].frag_stride != PAGE_SIZE);
+
+	/* Considering the above assumptions a fragment maps to a single
+	 * xsk_buff.
+	 */
+	for (i = 0; i < mlx5_wq_cyc_get_size(&rq->wqe.wq); i++)
+		rq->wqe.frags[i].xskp = &rq->wqe.alloc_units->xsk_buffs[i];
+}
+
+static int mlx5e_init_wqe_alloc_info(struct mlx5e_rq *rq, int node)
 {
+	int wq_sz = mlx5_wq_cyc_get_size(&rq->wqe.wq);
 	int len = wq_sz << rq->wqe.info.log_num_frags;
+	struct mlx5e_wqe_frag_info *frags;
+	union mlx5e_alloc_units *aus;
+	int aus_sz;
+
+	if (rq->xsk_pool)
+		aus_sz = sizeof(*aus->xsk_buffs);
+	else
+		aus_sz = sizeof(*aus->pages);
+
+	aus = kvzalloc_node(array_size(len, aus_sz), GFP_KERNEL, node);
+	if (!aus)
+		return -ENOMEM;
 
-	rq->wqe.alloc_units = kvzalloc_node(array_size(len, sizeof(*rq->wqe.alloc_units)),
-					    GFP_KERNEL, node);
-	if (!rq->wqe.alloc_units)
+	frags = kvzalloc_node(array_size(len, sizeof(*frags)), GFP_KERNEL, node);
+	if (!frags) {
+		kvfree(aus);
 		return -ENOMEM;
+	}
+
+	rq->wqe.alloc_units = aus;
+	rq->wqe.frags = frags;
 
-	mlx5e_init_frags_partition(rq);
+	if (rq->xsk_pool)
+		mlx5e_init_xsk_buffs(rq);
+	else
+		mlx5e_init_frags_partition(rq);
 
 	return 0;
 }
 
-static void mlx5e_free_au_list(struct mlx5e_rq *rq)
+static void mlx5e_free_wqe_alloc_info(struct mlx5e_rq *rq)
 {
+	kvfree(rq->wqe.frags);
 	kvfree(rq->wqe.alloc_units);
 }
 
@@ -778,18 +810,9 @@ static int mlx5e_alloc_rq(struct mlx5e_params *params,
 		rq->wqe.info = rqp->frags_info;
 		rq->buff.frame0_sz = rq->wqe.info.arr[0].frag_stride;
 
-		rq->wqe.frags =
-			kvzalloc_node(array_size(sizeof(*rq->wqe.frags),
-					(wq_sz << rq->wqe.info.log_num_frags)),
-				      GFP_KERNEL, node);
-		if (!rq->wqe.frags) {
-			err = -ENOMEM;
-			goto err_rq_wq_destroy;
-		}
-
-		err = mlx5e_init_au_list(rq, wq_sz, node);
+		err = mlx5e_init_wqe_alloc_info(rq, node);
 		if (err)
-			goto err_rq_frags;
+			goto err_rq_wq_destroy;
 	}
 
 	if (xsk) {
@@ -888,9 +911,7 @@ static int mlx5e_alloc_rq(struct mlx5e_params *params,
 		mlx5e_free_mpwqe_rq_drop_page(rq);
 		break;
 	default: /* MLX5_WQ_TYPE_CYCLIC */
-		mlx5e_free_au_list(rq);
-err_rq_frags:
-		kvfree(rq->wqe.frags);
+		mlx5e_free_wqe_alloc_info(rq);
 	}
 err_rq_wq_destroy:
 	mlx5_wq_destroy(&rq->wq_ctrl);
@@ -921,8 +942,7 @@ static void mlx5e_free_rq(struct mlx5e_rq *rq)
 		mlx5e_rq_free_shampo(rq);
 		break;
 	default: /* MLX5_WQ_TYPE_CYCLIC */
-		kvfree(rq->wqe.frags);
-		mlx5e_free_au_list(rq);
+		mlx5e_free_wqe_alloc_info(rq);
 	}
 
 	for (i = rq->page_cache.head; i != rq->page_cache.tail;

drivers/net/ethernet/mellanox/mlx5/core/en_rx.c

@@ -371,12 +371,12 @@ static inline int mlx5e_get_rx_frag(struct mlx5e_rq *rq,
 	int err = 0;
 
 	if (!frag->offset)
-		/* On first frag (offset == 0), replenish page (alloc_unit actually).
-		 * Other frags that point to the same alloc_unit (with a different
+		/* On first frag (offset == 0), replenish page.
+		 * Other frags that point to the same page (with a different
 		 * offset) should just use the new one without replenishing again
 		 * by themselves.
 		 */
-		err = mlx5e_page_alloc_pool(rq, &frag->au->page);
+		err = mlx5e_page_alloc_pool(rq, frag->pagep);
 
 	return err;
 }
@@ -386,7 +386,7 @@ static inline void mlx5e_put_rx_frag(struct mlx5e_rq *rq,
 				     bool recycle)
 {
 	if (frag->last_in_page)
-		mlx5e_page_release_dynamic(rq, frag->au->page, recycle);
+		mlx5e_page_release_dynamic(rq, *frag->pagep, recycle);
 }
 
 static inline struct mlx5e_wqe_frag_info *get_frag(struct mlx5e_rq *rq, u16 ix)
@@ -410,7 +410,7 @@ static int mlx5e_alloc_rx_wqe(struct mlx5e_rq *rq, struct mlx5e_rx_wqe_cyc *wqe,
 			goto free_frags;
 
 		headroom = i == 0 ? rq->buff.headroom : 0;
-		addr = page_pool_get_dma_addr(frag->au->page);
+		addr = page_pool_get_dma_addr(*frag->pagep);
 		wqe->data[i].addr = cpu_to_be64(addr + frag->offset + headroom);
 	}
 
@@ -434,7 +434,7 @@ static inline void mlx5e_free_rx_wqe(struct mlx5e_rq *rq,
 		 * put into the Reuse Ring, because there is no way to return
 		 * the page to the userspace when the interface goes down.
 		 */
-		xsk_buff_free(wi->au->xsk);
+		xsk_buff_free(*wi->xskp);
 		return;
 	}
 
@@ -1587,8 +1587,8 @@ static struct sk_buff *
 mlx5e_skb_from_cqe_linear(struct mlx5e_rq *rq, struct mlx5e_wqe_frag_info *wi,
 			  struct mlx5_cqe64 *cqe, u32 cqe_bcnt)
 {
-	union mlx5e_alloc_unit *au = wi->au;
 	u16 rx_headroom = rq->buff.headroom;
+	struct page *page = *wi->pagep;
 	struct bpf_prog *prog;
 	struct sk_buff *skb;
 	u32 metasize = 0;
@@ -1596,11 +1596,11 @@ mlx5e_skb_from_cqe_linear(struct mlx5e_rq *rq, struct mlx5e_wqe_frag_info *wi,
 	dma_addr_t addr;
 	u32 frag_size;
 
-	va             = page_address(au->page) + wi->offset;
+	va             = page_address(page) + wi->offset;
 	data           = va + rx_headroom;
 	frag_size      = MLX5_SKB_FRAG_SZ(rx_headroom + cqe_bcnt);
 
-	addr = page_pool_get_dma_addr(au->page);
+	addr = page_pool_get_dma_addr(page);
 	dma_sync_single_range_for_cpu(rq->pdev, addr, wi->offset,
 				      frag_size, rq->buff.map_dir);
 	net_prefetch(data);
@@ -1624,7 +1624,7 @@ mlx5e_skb_from_cqe_linear(struct mlx5e_rq *rq, struct mlx5e_wqe_frag_info *wi,
 		return NULL;
 
 	/* queue up for recycling/reuse */
-	page_ref_inc(au->page);
+	page_ref_inc(page);
 
 	return skb;
 }
@@ -1635,8 +1635,8 @@ mlx5e_skb_from_cqe_nonlinear(struct mlx5e_rq *rq, struct mlx5e_wqe_frag_info *wi
 {
 	struct mlx5e_rq_frag_info *frag_info = &rq->wqe.info.arr[0];
 	struct mlx5e_wqe_frag_info *head_wi = wi;
-	union mlx5e_alloc_unit *au = wi->au;
 	u16 rx_headroom = rq->buff.headroom;
+	struct page *page = *wi->pagep;
 	struct skb_shared_info *sinfo;
 	struct mlx5e_xdp_buff mxbuf;
 	u32 frag_consumed_bytes;
@@ -1646,10 +1646,10 @@ mlx5e_skb_from_cqe_nonlinear(struct mlx5e_rq *rq, struct mlx5e_wqe_frag_info *wi
 	u32 truesize;
 	void *va;
 
-	va = page_address(au->page) + wi->offset;
+	va = page_address(page) + wi->offset;
 	frag_consumed_bytes = min_t(u32, frag_info->frag_size, cqe_bcnt);
 
-	addr = page_pool_get_dma_addr(au->page);
+	addr = page_pool_get_dma_addr(page);
 	dma_sync_single_range_for_cpu(rq->pdev, addr, wi->offset,
 				      rq->buff.frame0_sz, rq->buff.map_dir);
 	net_prefetchw(va); /* xdp_frame data area */
@@ -1666,11 +1666,11 @@ mlx5e_skb_from_cqe_nonlinear(struct mlx5e_rq *rq, struct mlx5e_wqe_frag_info *wi
 	while (cqe_bcnt) {
 		skb_frag_t *frag;
 
-		au = wi->au;
+		page = *wi->pagep;
 
 		frag_consumed_bytes = min_t(u32, frag_info->frag_size, cqe_bcnt);
 
-		addr = page_pool_get_dma_addr(au->page);
+		addr = page_pool_get_dma_addr(page);
 		dma_sync_single_for_cpu(rq->pdev, addr + wi->offset,
 					frag_consumed_bytes, rq->buff.map_dir);
 
@@ -1684,11 +1684,11 @@ mlx5e_skb_from_cqe_nonlinear(struct mlx5e_rq *rq, struct mlx5e_wqe_frag_info *wi
 		}
 
 		frag = &sinfo->frags[sinfo->nr_frags++];
-		__skb_frag_set_page(frag, au->page);
+		__skb_frag_set_page(frag, page);
 		skb_frag_off_set(frag, wi->offset);
 		skb_frag_size_set(frag, frag_consumed_bytes);
 
-		if (page_is_pfmemalloc(au->page))
+		if (page_is_pfmemalloc(page))
 			xdp_buff_set_frag_pfmemalloc(&mxbuf.xdp);
 
 		sinfo->xdp_frags_size += frag_consumed_bytes;
@@ -1717,7 +1717,7 @@ mlx5e_skb_from_cqe_nonlinear(struct mlx5e_rq *rq, struct mlx5e_wqe_frag_info *wi
 	if (unlikely(!skb))
 		return NULL;
 
-	page_ref_inc(head_wi->au->page);
+	page_ref_inc(*head_wi->pagep);
 
 	if (xdp_buff_has_frags(&mxbuf.xdp)) {
 		int i;