[RFC,v2,05/11] memory-provider: implement dmabuf devmem memory provider

diff --git a/include/net/page_pool.h b/include/net/page_pool.h
index e395f82e182b..537eb36115ed 100644
--- a/include/net/page_pool.h
+++ b/include/net/page_pool.h
@@ -32,6 +32,7 @@ 
 #include <linux/mm.h> /* Needed by ptr_ring */
 #include <linux/ptr_ring.h>
 #include <linux/dma-direction.h>
+#include <net/net_debug.h>

 #define PP_FLAG_DMA_MAP		BIT(0) /* Should page_pool do the DMA
 					* map/unmap
@@ -157,6 +158,7 @@  enum pp_memory_provider_type {
 	PP_MP_HUGE_SPLIT, /* 2MB, online page alloc */
 	PP_MP_HUGE, /* 2MB, all memory pre-allocated */
 	PP_MP_HUGE_1G, /* 1G pages, MEP, pre-allocated */
+	PP_MP_DMABUF_DEVMEM, /* dmabuf devmem provider */
 };

 struct pp_memory_provider_ops {
@@ -170,9 +172,15 @@  extern const struct pp_memory_provider_ops basic_ops;
 extern const struct pp_memory_provider_ops hugesp_ops;
 extern const struct pp_memory_provider_ops huge_ops;
 extern const struct pp_memory_provider_ops huge_1g_ops;
+extern const struct pp_memory_provider_ops dmabuf_devmem_ops;

 /* page_pool_iov support */

+/*  We overload the LSB of the struct page pointer to indicate whether it's
+ *  a page or page_pool_iov.
+ */
+#define PP_DEVMEM 0x01UL
+
 /* Owner of the dma-buf chunks inserted into the gen pool. Each scatterlist
  * entry from the dmabuf is inserted into the genpool as a chunk, and needs
  * this owner struct to keep track of some metadata necessary to create
@@ -196,6 +204,8 @@  struct page_pool_iov {
 	struct dmabuf_genpool_chunk_owner *owner;

 	refcount_t refcount;
+
+	struct page_pool *pp;
 };

 static inline struct dmabuf_genpool_chunk_owner *
@@ -218,12 +228,60 @@  page_pool_iov_dma_addr(const struct page_pool_iov *ppiov)
 	       ((dma_addr_t)page_pool_iov_idx(ppiov) << PAGE_SHIFT);
 }

+static inline unsigned long
+page_pool_iov_virtual_addr(const struct page_pool_iov *ppiov)
+{
+	struct dmabuf_genpool_chunk_owner *owner = page_pool_iov_owner(ppiov);
+
+	return owner->base_virtual +
+	       ((unsigned long)page_pool_iov_idx(ppiov) << PAGE_SHIFT);
+}
+
 static inline struct netdev_dmabuf_binding *
 page_pool_iov_binding(const struct page_pool_iov *ppiov)
 {
 	return page_pool_iov_owner(ppiov)->binding;
 }

+static inline int page_pool_iov_refcount(const struct page_pool_iov *ppiov)
+{
+	return refcount_read(&ppiov->refcount);
+}
+
+static inline void page_pool_iov_get_many(struct page_pool_iov *ppiov,
+					  unsigned int count)
+{
+	refcount_add(count, &ppiov->refcount);
+}
+
+void __page_pool_iov_free(struct page_pool_iov *ppiov);
+
+static inline void page_pool_iov_put_many(struct page_pool_iov *ppiov,
+					  unsigned int count)
+{
+	if (!refcount_sub_and_test(count, &ppiov->refcount))
+		return;
+
+	__page_pool_iov_free(ppiov);
+}
+
+/* page pool mm helpers */
+
+static inline bool page_is_page_pool_iov(const struct page *page)
+{
+	return (unsigned long)page & PP_DEVMEM;
+}
+
+static inline struct page_pool_iov *page_to_page_pool_iov(struct page *page)
+{
+	if (page_is_page_pool_iov(page))
+		return (struct page_pool_iov *)((unsigned long)page &
+						~PP_DEVMEM);
+
+	DEBUG_NET_WARN_ON_ONCE(true);
+	return NULL;
+}
+
 struct page_pool {
 	struct page_pool_params p;

diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index df3f431fcff3..0a7c08d748b8 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -20,6 +20,7 @@ 
 #include <linux/poison.h>
 #include <linux/ethtool.h>
 #include <linux/netdevice.h>
+#include <linux/genalloc.h>

 #include <trace/events/page_pool.h>

@@ -236,6 +237,9 @@  static int page_pool_init(struct page_pool *pool,
 	case PP_MP_HUGE_1G:
 		pool->mp_ops = &huge_1g_ops;
 		break;
+	case PP_MP_DMABUF_DEVMEM:
+		pool->mp_ops = &dmabuf_devmem_ops;
+		break;
 	default:
 		err = -EINVAL;
 		goto free_ptr_ring;
@@ -1006,6 +1010,15 @@  bool page_pool_return_skb_page(struct page *page, bool napi_safe)
 }
 EXPORT_SYMBOL(page_pool_return_skb_page);

+void __page_pool_iov_free(struct page_pool_iov *ppiov)
+{
+	if (ppiov->pp->mp_ops != &dmabuf_devmem_ops)
+		return;
+
+	netdev_free_devmem(ppiov);
+}
+EXPORT_SYMBOL_GPL(__page_pool_iov_free);
+
 /***********************
  *  Mem provider hack  *
  ***********************/
@@ -1538,3 +1551,69 @@  const struct pp_memory_provider_ops huge_1g_ops = {
 	.alloc_pages		= mp_huge_1g_alloc_pages,
 	.release_page		= mp_huge_1g_release,
 };
+
+/*** "Dmabuf devmem memory provider" ***/
+
+static int mp_dmabuf_devmem_init(struct page_pool *pool)
+{
+	struct netdev_dmabuf_binding *binding = pool->mp_priv;
+
+	if (!binding)
+		return -EINVAL;
+
+	if (pool->p.flags & PP_FLAG_DMA_MAP ||
+	    pool->p.flags & PP_FLAG_DMA_SYNC_DEV ||
+	    pool->p.flags & PP_FLAG_PAGE_FRAG)
+		return -EOPNOTSUPP;
+
+	netdev_devmem_binding_get(binding);
+	return 0;
+}
+
+static struct page *mp_dmabuf_devmem_alloc_pages(struct page_pool *pool,
+						 gfp_t gfp)
+{
+	struct netdev_dmabuf_binding *binding = pool->mp_priv;
+	struct page_pool_iov *ppiov;
+
+	ppiov = netdev_alloc_devmem(binding);
+	if (!ppiov)
+		return NULL;
+
+	ppiov->pp = pool;
+	pool->pages_state_hold_cnt++;
+	trace_page_pool_state_hold(pool, (struct page *)ppiov,
+				   pool->pages_state_hold_cnt);
+	ppiov = (struct page_pool_iov *)((unsigned long)ppiov | PP_DEVMEM);
+
+	return (struct page *)ppiov;
+}
+
+static void mp_dmabuf_devmem_destroy(struct page_pool *pool)
+{
+	struct netdev_dmabuf_binding *binding = pool->mp_priv;
+
+	netdev_devmem_binding_put(binding);
+}
+
+static bool mp_dmabuf_devmem_release_page(struct page_pool *pool,
+					  struct page *page)
+{
+	struct page_pool_iov *ppiov;
+
+	if (WARN_ON_ONCE(!page_is_page_pool_iov(page)))
+		return false;
+
+	ppiov = page_to_page_pool_iov(page);
+	page_pool_iov_put_many(ppiov, 1);
+	/* We don't want the page pool put_page()ing our page_pool_iovs. */
+	return false;
+}
+
+const struct pp_memory_provider_ops dmabuf_devmem_ops = {
+	.init			= mp_dmabuf_devmem_init,
+	.destroy		= mp_dmabuf_devmem_destroy,
+	.alloc_pages		= mp_dmabuf_devmem_alloc_pages,
+	.release_page		= mp_dmabuf_devmem_release_page,
+};
+EXPORT_SYMBOL(dmabuf_devmem_ops);