[RFC PATCH v2 03/11] netdev: implement netdevice devmem allocator

[Mina Almasry]

Implement netdev devmem allocator. The allocator takes a given struct
netdev_dmabuf_binding as input and allocates page_pool_iov from that
binding.

The allocation simply delegates to the binding's genpool for the
allocation logic and wraps the returned memory region in a page_pool_iov
struct.

page_pool_iov are refcounted and are freed back to the binding when the
refcount drops to 0.

Signed-off-by: Willem de Bruijn <willemb at google.com>
Signed-off-by: Kaiyuan Zhang <kaiyuanz at google.com>

Signed-off-by: Mina Almasry <almasrymina at google.com>
---
 include/linux/netdevice.h |  4 ++++
 include/net/page_pool.h   | 26 ++++++++++++++++++++++++++
 net/core/dev.c            | 36 ++++++++++++++++++++++++++++++++++++
 3 files changed, 66 insertions(+)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 1b7c5966d2ca..bb5296e6cb00 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -5078,6 +5078,10 @@ void netif_set_tso_max_segs(struct net_device *dev, unsigned int segs);
 void netif_inherit_tso_max(struct net_device *to,
 			   const struct net_device *from);

+struct page_pool_iov *
+netdev_alloc_devmem(struct netdev_dmabuf_binding *binding);
+void netdev_free_devmem(struct page_pool_iov *ppiov);
+
 void netdev_unbind_dmabuf_to_queue(struct netdev_dmabuf_binding *binding);
 int netdev_bind_dmabuf_to_queue(struct net_device *dev, unsigned int dmabuf_fd,
 				u32 rxq_idx,
diff --git a/include/net/page_pool.h b/include/net/page_pool.h
index 61b2066d32b5..13ae7f668c9e 100644
--- a/include/net/page_pool.h
+++ b/include/net/page_pool.h
@@ -197,6 +197,32 @@ struct page_pool_iov {
 	refcount_t refcount;
 };

+static inline struct dmabuf_genpool_chunk_owner *
+page_pool_iov_owner(const struct page_pool_iov *ppiov)
+{
+	return ppiov->owner;
+}
+
+static inline unsigned int page_pool_iov_idx(const struct page_pool_iov *ppiov)
+{
+	return ppiov - page_pool_iov_owner(ppiov)->ppiovs;
+}
+
+static inline dma_addr_t
+page_pool_iov_dma_addr(const struct page_pool_iov *ppiov)
+{
+	struct dmabuf_genpool_chunk_owner *owner = page_pool_iov_owner(ppiov);
+
+	return owner->base_dma_addr +
+	       ((dma_addr_t)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;
+}
+
 struct page_pool {
 	struct page_pool_params p;

diff --git a/net/core/dev.c b/net/core/dev.c
index 02a25ccf771a..0149335a25b7 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2072,6 +2072,42 @@ void __netdev_devmem_binding_free(struct netdev_dmabuf_binding *binding)
 	kfree(binding);
 }

+struct page_pool_iov *netdev_alloc_devmem(struct netdev_dmabuf_binding *binding)
+{
+	struct dmabuf_genpool_chunk_owner *owner;
+	struct page_pool_iov *ppiov;
+	unsigned long dma_addr;
+	ssize_t offset;
+	ssize_t index;
+
+	dma_addr = gen_pool_alloc_owner(binding->chunk_pool, PAGE_SIZE,
+					(void **)&owner);
+	if (!dma_addr)
+		return NULL;
+
+	offset = dma_addr - owner->base_dma_addr;
+	index = offset / PAGE_SIZE;
+	ppiov = &owner->ppiovs[index];
+
+	netdev_devmem_binding_get(binding);
+
+	return ppiov;
+}
+
+void netdev_free_devmem(struct page_pool_iov *ppiov)
+{
+	struct netdev_dmabuf_binding *binding = page_pool_iov_binding(ppiov);
+
+	refcount_set(&ppiov->refcount, 1);
+
+	if (gen_pool_has_addr(binding->chunk_pool,
+			      page_pool_iov_dma_addr(ppiov), PAGE_SIZE))
+		gen_pool_free(binding->chunk_pool,
+			      page_pool_iov_dma_addr(ppiov), PAGE_SIZE);
+
+	netdev_devmem_binding_put(binding);
+}
+
 void netdev_unbind_dmabuf_to_queue(struct netdev_dmabuf_binding *binding)
 {
 	struct netdev_rx_queue *rxq;
--
2.41.0.640.ga95def55d0-goog