Re: [PATCH net-next v24 06/13] memory-provider: dmabuf devmem memory provider

diff --git a/include/net/mp_dmabuf_devmem.h b/include/net/mp_dmabuf_devmem.h
new file mode 100644
index 000000000000..6d1cf2a77f6b
--- /dev/null
+++ b/include/net/mp_dmabuf_devmem.h

@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Dmabuf device memory provider.
+ *
+ * Authors:	Mina Almasry <almasrymina@google.com>
+ *
+ */
+#ifndef _NET_MP_DMABUF_DEVMEM_H
+#define _NET_MP_DMABUF_DEVMEM_H
+
+#include <net/netmem.h>
+
+#if defined(CONFIG_NET_DEVMEM)
+int mp_dmabuf_devmem_init(struct page_pool *pool);
+
+netmem_ref mp_dmabuf_devmem_alloc_netmems(struct page_pool *pool, gfp_t gfp);
+
+void mp_dmabuf_devmem_destroy(struct page_pool *pool);
+
+bool mp_dmabuf_devmem_release_page(struct page_pool *pool, netmem_ref netmem);
+#else
+static inline int mp_dmabuf_devmem_init(struct page_pool *pool)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline netmem_ref mp_dmabuf_devmem_alloc_netmems(struct page_pool *pool,
+							gfp_t gfp)

+{
+	return 0;
+}
+
+static inline void mp_dmabuf_devmem_destroy(struct page_pool *pool)
+{
+}
+
+static inline bool mp_dmabuf_devmem_release_page(struct page_pool *pool,
+						 netmem_ref netmem)
+{
+	return false;
+}
+#endif
+
+#endif /* _NET_MP_DMABUF_DEVMEM_H */

diff --git a/include/net/netmem.h b/include/net/netmem.h
index ac6c7945117b..61400d4b0d66 100644
--- a/include/net/netmem.h
+++ b/include/net/netmem.h

@@ -8,6 +8,7 @@
 #ifndef _NET_NETMEM_H
 #define _NET_NETMEM_H
 
+#include <linux/mm.h>
 #include <net/devmem.h>
 #include <net/net_debug.h>
 

diff --git a/include/net/page_pool/types.h b/include/net/page_pool/types.h
index 4afd6dd56351..1b4698710f25 100644
--- a/include/net/page_pool/types.h
+++ b/include/net/page_pool/types.h

@@ -20,8 +20,17 @@
 					* device driver responsibility
 					*/
 #define PP_FLAG_SYSTEM_POOL	BIT(2) /* Global system page_pool */
+#define PP_FLAG_ALLOW_UNREADABLE_NETMEM	BIT(3) /* Allow unreadable (net_iov
+						* backed) netmem in this
+						* page_pool. Drivers setting
+						* this must be able to support
+						* unreadable netmem, where
+						* netmem_address() would return
+						* NULL. This flag should not be
+						* set for header page_pools.
+						*/

 #define PP_FLAG_ALL		(PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV | \
-				 PP_FLAG_SYSTEM_POOL)
+				 PP_FLAG_SYSTEM_POOL | PP_FLAG_ALLOW_UNREADABLE_NETMEM)
 
 /*
  * Fast allocation side cache array/stack

@@ -57,7 +66,9 @@ struct pp_alloc_cache {
  * @offset:	DMA sync address offset for PP_FLAG_DMA_SYNC_DEV
  * @slow:	params with slowpath access only (initialization and Netlink)
  * @netdev:	netdev this pool will serve (leave as NULL if none or multiple)
- * @flags:	PP_FLAG_DMA_MAP, PP_FLAG_DMA_SYNC_DEV, PP_FLAG_SYSTEM_POOL
+ * @queue:	struct netdev_rx_queue this page_pool is being created for.
+ * @flags:	PP_FLAG_DMA_MAP, PP_FLAG_DMA_SYNC_DEV, PP_FLAG_SYSTEM_POOL,
+ *		PP_FLAG_ALLOW_UNREADABLE_NETMEM.
  */
 struct page_pool_params {
 	struct_group_tagged(page_pool_params_fast, fast,

@@ -72,6 +83,7 @@ struct page_pool_params {
 	);
 	struct_group_tagged(page_pool_params_slow, slow,
 		struct net_device *netdev;
+		struct netdev_rx_queue *queue;

 		unsigned int	flags;
 /* private: used by test code only */
 		void (*init_callback)(netmem_ref netmem, void *arg);

diff --git a/net/core/devmem.c b/net/core/devmem.c
index 727e5ee39f30..c8c112360caa 100644
--- a/net/core/devmem.c
+++ b/net/core/devmem.c

@@ -13,6 +13,7 @@
 #include <linux/netdevice.h>
 #include <linux/types.h>
 #include <net/devmem.h>
+#include <net/mp_dmabuf_devmem.h>
 #include <net/netdev_queues.h>
 #include <net/netdev_rx_queue.h>
 #include <net/page_pool/helpers.h>

@@ -320,3 +321,68 @@ void dev_dmabuf_uninstall(struct net_device *dev)
 			}
 	}
 }
+
+/*** "Dmabuf devmem memory provider" ***/
+
+int mp_dmabuf_devmem_init(struct page_pool *pool)
+{
+	struct net_devmem_dmabuf_binding *binding = pool->mp_priv;
+
+	if (!binding)
+		return -EINVAL;
+
+	if (!pool->dma_map)
+		return -EOPNOTSUPP;
+
+	if (pool->dma_sync)
+		return -EOPNOTSUPP;
+
+	if (pool->p.order != 0)
+		return -E2BIG;
+
+	net_devmem_dmabuf_binding_get(binding);
+	return 0;
+}
+
+netmem_ref mp_dmabuf_devmem_alloc_netmems(struct page_pool *pool, gfp_t gfp)
+{
+	struct net_devmem_dmabuf_binding *binding = pool->mp_priv;
+	netmem_ref netmem;
+	struct net_iov *niov;

+	niov = net_devmem_alloc_dmabuf(binding);
+	if (!niov)
+		return 0;
+
+	netmem = net_iov_to_netmem(niov);
+
+	page_pool_set_pp_info(pool, netmem);
+
+	pool->pages_state_hold_cnt++;
+	trace_page_pool_state_hold(pool, netmem, pool->pages_state_hold_cnt);
+	return netmem;
+}
+
+void mp_dmabuf_devmem_destroy(struct page_pool *pool)
+{
+	struct net_devmem_dmabuf_binding *binding = pool->mp_priv;
+
+	net_devmem_dmabuf_binding_put(binding);
+}
+
+bool mp_dmabuf_devmem_release_page(struct page_pool *pool, netmem_ref netmem)
+{
+	if (WARN_ON_ONCE(!netmem_is_net_iov(netmem)))
+		return false;
+
+	if (WARN_ON_ONCE(atomic_long_read(netmem_get_pp_ref_count_ref(netmem)) !=
+		     1))

+		return false;
+
+	page_pool_clear_pp_info(netmem);
+
+	net_devmem_free_dmabuf(netmem_to_net_iov(netmem));
+
+	/* We don't want the page pool put_page()ing our net_iovs. */
+	return false;
+}

diff --git a/net/core/netdev_rx_queue.c b/net/core/netdev_rx_queue.c
index da11720a5983..e217a5838c87 100644
--- a/net/core/netdev_rx_queue.c
+++ b/net/core/netdev_rx_queue.c

@@ -4,8 +4,11 @@
 #include <net/netdev_queues.h>
 #include <net/netdev_rx_queue.h>
 
+#include "page_pool_priv.h"
+
 int netdev_rx_queue_restart(struct net_device *dev, unsigned int rxq_idx)
 {
+	struct netdev_rx_queue *rxq = __netif_get_rx_queue(dev, rxq_idx);
 	void *new_mem, *old_mem;
 	int err;
 

@@ -31,6 +34,10 @@ int netdev_rx_queue_restart(struct net_device *dev, unsigned int rxq_idx)
 	if (err)
 		goto err_free_old_mem;
 
+	err = page_pool_check_memory_provider(dev, rxq);
+	if (err)
+		goto err_free_new_queue_mem;
+
 	err = dev->queue_mgmt_ops->ndo_queue_stop(dev, old_mem, rxq_idx);
 	if (err)
 		goto err_free_new_queue_mem;

diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index 52659db2d765..6e24950f2be4 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c

@@ -11,6 +11,8 @@
 #include <linux/slab.h>
 #include <linux/device.h>
 
+#include <net/mp_dmabuf_devmem.h>
+#include <net/netdev_rx_queue.h>
 #include <net/page_pool/helpers.h>
 #include <net/xdp.h>
 

@@ -190,6 +192,7 @@ static int page_pool_init(struct page_pool *pool,
 			  int cpuid)
 {
 	unsigned int ring_qsize = 1024; /* Default */
+	int err;
 
 	page_pool_struct_check();
 

@@ -271,7 +274,36 @@ static int page_pool_init(struct page_pool *pool,
 	if (pool->dma_map)
 		get_device(pool->p.dev);
 
+	if (pool->slow.queue &&
+	    pool->slow.flags & PP_FLAG_ALLOW_UNREADABLE_NETMEM) {
+		/* We rely on rtnl_lock()ing to make sure netdev_rx_queue
+		 * configuration doesn't change while we're initializing the

+		 * page_pool.
+		 */
+		ASSERT_RTNL();
+		pool->mp_priv = pool->slow.queue->mp_params.mp_priv;
+	}