[RFC PATCH net-next v5 05/14] netdev: netdevice devmem allocator

[Mina Almasry <almasrymina@google.com>]

Implement netdev devmem allocator. The allocator takes a given struct
netdev_dmabuf_binding as input and allocates net_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 net_iov
struct.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Kaiyuan Zhang <kaiyuanz@google.com>
Signed-off-by: Mina Almasry <almasrymina@google.com>

---

v1:
- Rename devmem -> dmabuf (David).

---
 include/net/devmem.h | 12 ++++++++++++
 include/net/netmem.h | 26 ++++++++++++++++++++++++++
 net/core/dev.c       | 38 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 76 insertions(+)

diff --git a/include/net/devmem.h b/include/net/devmem.h
index 85ccbbe84c65..4207adadc2bb 100644
--- a/include/net/devmem.h
+++ b/include/net/devmem.h
@@ -67,6 +67,8 @@ struct dmabuf_genpool_chunk_owner {
 };
 
 #ifdef CONFIG_DMA_SHARED_BUFFER
+struct net_iov *netdev_alloc_dmabuf(struct netdev_dmabuf_binding *binding);
+void netdev_free_dmabuf(struct net_iov *ppiov);
 void __netdev_dmabuf_binding_free(struct netdev_dmabuf_binding *binding);
 int netdev_bind_dmabuf(struct net_device *dev, unsigned int dmabuf_fd,
 		       struct netdev_dmabuf_binding **out);
@@ -74,6 +76,16 @@ void netdev_unbind_dmabuf(struct netdev_dmabuf_binding *binding);
 int netdev_bind_dmabuf_to_queue(struct net_device *dev, u32 rxq_idx,
 				struct netdev_dmabuf_binding *binding);
 #else
+static inline struct net_iov *
+netdev_alloc_dmabuf(struct netdev_dmabuf_binding *binding)
+{
+	return NULL;
+}
+
+static inline void netdev_free_dmabuf(struct net_iov *ppiov)
+{
+}
+
 static inline void
 __netdev_dmabuf_binding_free(struct netdev_dmabuf_binding *binding)
 {
diff --git a/include/net/netmem.h b/include/net/netmem.h
index 45eb42d9990b..7fce2efc8707 100644
--- a/include/net/netmem.h
+++ b/include/net/netmem.h
@@ -14,8 +14,34 @@
 
 struct net_iov {
 	struct dmabuf_genpool_chunk_owner *owner;
+	unsigned long dma_addr;
 };
 
+static inline struct dmabuf_genpool_chunk_owner *
+net_iov_owner(const struct net_iov *niov)
+{
+	return niov->owner;
+}
+
+static inline unsigned int net_iov_idx(const struct net_iov *niov)
+{
+	return niov - net_iov_owner(niov)->niovs;
+}
+
+static inline dma_addr_t net_iov_dma_addr(const struct net_iov *niov)
+{
+	struct dmabuf_genpool_chunk_owner *owner = net_iov_owner(niov);
+
+	return owner->base_dma_addr +
+	       ((dma_addr_t)net_iov_idx(niov) << PAGE_SHIFT);
+}
+
+static inline struct netdev_dmabuf_binding *
+net_iov_binding(const struct net_iov *niov)
+{
+	return net_iov_owner(niov)->binding;
+}
+
 /* netmem */
 
 struct netmem {
diff --git a/net/core/dev.c b/net/core/dev.c
index 2e474099267a..20ba528ef426 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2119,6 +2119,44 @@ static int netdev_restart_rx_queue(struct net_device *dev, int rxq_idx)
 	return err;
 }
 
+struct net_iov *netdev_alloc_dmabuf(struct netdev_dmabuf_binding *binding)
+{
+	struct dmabuf_genpool_chunk_owner *owner;
+	unsigned long dma_addr;
+	struct net_iov *niov;
+	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;
+	niov = &owner->niovs[index];
+
+	niov->pp_magic = 0;
+	niov->pp = NULL;
+	niov->dma_addr = 0;
+	atomic_long_set(&niov->pp_ref_count, 0);
+
+	netdev_dmabuf_binding_get(binding);
+
+	return niov;
+}
+
+void netdev_free_dmabuf(struct net_iov *niov)
+{
+	struct netdev_dmabuf_binding *binding = net_iov_binding(niov);
+	unsigned long dma_addr = net_iov_dma_addr(niov);
+
+	if (gen_pool_has_addr(binding->chunk_pool, dma_addr, PAGE_SIZE))
+		gen_pool_free(binding->chunk_pool, dma_addr, PAGE_SIZE);
+
+	netdev_dmabuf_binding_put(binding);
+}
+
 /* Protected by rtnl_lock() */
 static DEFINE_XARRAY_FLAGS(netdev_dmabuf_bindings, XA_FLAGS_ALLOC1);
 
-- 
2.43.0.472.g3155946c3a-goog