[PATCH net-next v11 15/21] io_uring/zcrx: dma-map area for the device

[David Wei <dw@davidwei.uk>]

From: Pavel Begunkov <asml.silence@gmail.com>

Setup DMA mappings for the area into which we intend to receive data
later on. We know the device we want to attach to even before we get a
page pool and can pre-map in advance. All net_iov are synchronised for
device when allocated, see page_pool_mp_return_in_cache().

Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: David Wei <dw@davidwei.uk>
---
 io_uring/zcrx.c | 82 ++++++++++++++++++++++++++++++++++++++++++++++++-
 io_uring/zcrx.h |  1 +
 2 files changed, 82 insertions(+), 1 deletion(-)

diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
index c007ff80b325..2b668f09b55f 100644
--- a/io_uring/zcrx.c
+++ b/io_uring/zcrx.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/kernel.h>
 #include <linux/errno.h>
+#include <linux/dma-map-ops.h>
 #include <linux/mm.h>
 #include <linux/nospec.h>
 #include <linux/io_uring.h>
@@ -21,6 +22,73 @@
 #include "zcrx.h"
 #include "rsrc.h"
 
+#define IO_DMA_ATTR (DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_WEAK_ORDERING)
+
+static void __io_zcrx_unmap_area(struct io_zcrx_ifq *ifq,
+				 struct io_zcrx_area *area, int nr_mapped)
+{
+	int i;
+
+	for (i = 0; i < nr_mapped; i++) {
+		struct net_iov *niov = &area->nia.niovs[i];
+		dma_addr_t dma;
+
+		dma = page_pool_get_dma_addr_netmem(net_iov_to_netmem(niov));
+		dma_unmap_page_attrs(ifq->dev, dma, PAGE_SIZE,
+				     DMA_FROM_DEVICE, IO_DMA_ATTR);
+		net_mp_niov_set_dma_addr(niov, 0);
+	}
+}
+
+static void io_zcrx_unmap_area(struct io_zcrx_ifq *ifq, struct io_zcrx_area *area)
+{
+	if (area->is_mapped)
+		__io_zcrx_unmap_area(ifq, area, area->nia.num_niovs);
+}
+
+static int io_zcrx_map_area(struct io_zcrx_ifq *ifq, struct io_zcrx_area *area)
+{
+	int i;
+
+	for (i = 0; i < area->nia.num_niovs; i++) {
+		struct net_iov *niov = &area->nia.niovs[i];
+		dma_addr_t dma;
+
+		dma = dma_map_page_attrs(ifq->dev, area->pages[i], 0, PAGE_SIZE,
+					 DMA_FROM_DEVICE, IO_DMA_ATTR);
+		if (dma_mapping_error(ifq->dev, dma))
+			break;
+		if (net_mp_niov_set_dma_addr(niov, dma)) {
+			dma_unmap_page_attrs(ifq->dev, dma, PAGE_SIZE,
+					     DMA_FROM_DEVICE, IO_DMA_ATTR);
+			break;
+		}
+	}
+
+	if (i != area->nia.num_niovs) {
+		__io_zcrx_unmap_area(ifq, area, i);
+		return -EINVAL;
+	}
+
+	area->is_mapped = true;
+	return 0;
+}
+
+static void io_zcrx_sync_for_device(const struct page_pool *pool,
+				    struct net_iov *niov)
+{
+#if defined(CONFIG_HAS_DMA) && defined(CONFIG_DMA_NEED_SYNC)
+	dma_addr_t dma_addr;
+
+	if (!dma_dev_need_sync(pool->p.dev))
+		return;
+
+	dma_addr = page_pool_get_dma_addr_netmem(net_iov_to_netmem(niov));
+	__dma_sync_single_for_device(pool->p.dev, dma_addr + pool->p.offset,
+				     PAGE_SIZE, pool->p.dma_dir);
+#endif
+}
+
 #define IO_RQ_MAX_ENTRIES		32768
 
 __maybe_unused
@@ -83,6 +151,8 @@ static void io_free_rbuf_ring(struct io_zcrx_ifq *ifq)
 
 static void io_zcrx_free_area(struct io_zcrx_area *area)
 {
+	io_zcrx_unmap_area(area->ifq, area);
+
 	kvfree(area->freelist);
 	kvfree(area->nia.niovs);
 	kvfree(area->user_refs);
@@ -272,6 +342,10 @@ int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
 		return -EOPNOTSUPP;
 	get_device(ifq->dev);
 
+	ret = io_zcrx_map_area(ifq, ifq->area);
+	if (ret)
+		goto err;
+
 	reg.offsets.rqes = sizeof(struct io_uring);
 	reg.offsets.head = offsetof(struct io_uring, head);
 	reg.offsets.tail = offsetof(struct io_uring, tail);
@@ -422,6 +496,7 @@ static void io_zcrx_ring_refill(struct page_pool *pp,
 			continue;
 		}
 
+		io_zcrx_sync_for_device(pp, niov);
 		net_mp_netmem_place_in_cache(pp, netmem);
 	} while (--entries);
 
@@ -439,6 +514,7 @@ static void io_zcrx_refill_slow(struct page_pool *pp, struct io_zcrx_ifq *ifq)
 		netmem_ref netmem = net_iov_to_netmem(niov);
 
 		net_mp_niov_set_page_pool(pp, niov);
+		io_zcrx_sync_for_device(pp, niov);
 		net_mp_netmem_place_in_cache(pp, netmem);
 	}
 	spin_unlock_bh(&area->freelist_lock);
@@ -482,10 +558,14 @@ static int io_pp_zc_init(struct page_pool *pp)
 
 	if (WARN_ON_ONCE(!ifq))
 		return -EINVAL;
-	if (pp->dma_map)
+	if (WARN_ON_ONCE(ifq->dev != pp->p.dev))
+		return -EINVAL;
+	if (WARN_ON_ONCE(!pp->dma_map))
 		return -EOPNOTSUPP;
 	if (pp->p.order != 0)
 		return -EOPNOTSUPP;
+	if (pp->p.dma_dir != DMA_FROM_DEVICE)
+		return -EOPNOTSUPP;
 
 	percpu_ref_get(&ifq->ctx->refs);
 	return 0;
diff --git a/io_uring/zcrx.h b/io_uring/zcrx.h
index 6c808240ac91..1b6363591f72 100644
--- a/io_uring/zcrx.h
+++ b/io_uring/zcrx.h
@@ -11,6 +11,7 @@ struct io_zcrx_area {
 	struct io_zcrx_ifq	*ifq;
 	atomic_t		*user_refs;
 
+	bool			is_mapped;
 	u16			area_id;
 	struct page		**pages;
 
-- 
2.43.5