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Date: Tue,  2 Apr 2024 17:20:42 -0700
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Subject: [RFC PATCH net-next v8 05/14] netdev: netdevice devmem allocator
From: Mina Almasry <almasrymina@google.com>
To: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, 
	linux-doc@vger.kernel.org, linux-alpha@vger.kernel.org, 
	linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, 
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Cc: Mina Almasry <almasrymina@google.com>, "David S. Miller" <davem@davemloft.net>, 
	Eric Dumazet <edumazet@google.com>, Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>, 
	Jonathan Corbet <corbet@lwn.net>, Richard Henderson <richard.henderson@linaro.org>, 
	Ivan Kokshaysky <ink@jurassic.park.msu.ru>, Matt Turner <mattst88@gmail.com>, 
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>, 
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	Andreas Larsson <andreas@gaisler.com>, Jesper Dangaard Brouer <hawk@kernel.org>, 
	Ilias Apalodimas <ilias.apalodimas@linaro.org>, Steven Rostedt <rostedt@goodmis.org>, 
	Masami Hiramatsu <mhiramat@kernel.org>, Mathieu Desnoyers <mathieu.desnoyers@efficios.com>, 
	Arnd Bergmann <arnd@arndb.de>, Alexei Starovoitov <ast@kernel.org>, Daniel Borkmann <daniel@iogearbox.net>, 
	Andrii Nakryiko <andrii@kernel.org>, Martin KaFai Lau <martin.lau@linux.dev>, 
	Eduard Zingerman <eddyz87@gmail.com>, Song Liu <song@kernel.org>, 
	Yonghong Song <yonghong.song@linux.dev>, John Fastabend <john.fastabend@gmail.com>, 
	KP Singh <kpsingh@kernel.org>, Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>, 
	Jiri Olsa <jolsa@kernel.org>, Steffen Klassert <steffen.klassert@secunet.com>, 
	Herbert Xu <herbert@gondor.apana.org.au>, David Ahern <dsahern@kernel.org>, 
	Willem de Bruijn <willemdebruijn.kernel@gmail.com>, Shuah Khan <shuah@kernel.org>, 
	Sumit Semwal <sumit.semwal@linaro.org>, 
	"=?UTF-8?q?Christian=20K=C3=B6nig?=" <christian.koenig@amd.com>, Amritha Nambiar <amritha.nambiar@intel.com>, 
	Maciej Fijalkowski <maciej.fijalkowski@intel.com>, 
	Alexander Mikhalitsyn <alexander@mihalicyn.com>, Kaiyuan Zhang <kaiyuanz@google.com>, 
	Christian Brauner <brauner@kernel.org>, Simon Horman <horms@kernel.org>, 
	David Howells <dhowells@redhat.com>, Florian Westphal <fw@strlen.de>, 
	Yunsheng Lin <linyunsheng@huawei.com>, Kuniyuki Iwashima <kuniyu@amazon.com>, Jens Axboe <axboe@kernel.dk>, 
	Arseniy Krasnov <avkrasnov@salutedevices.com>, 
	Aleksander Lobakin <aleksander.lobakin@intel.com>, Michael Lass <bevan@bi-co.net>, 
	Jiri Pirko <jiri@resnulli.us>, Sebastian Andrzej Siewior <bigeasy@linutronix.de>, 
	Lorenzo Bianconi <lorenzo@kernel.org>, Richard Gobert <richardbgobert@gmail.com>, 
	Sridhar Samudrala <sridhar.samudrala@intel.com>, Xuan Zhuo <xuanzhuo@linux.alibaba.com>, 
	Johannes Berg <johannes.berg@intel.com>, Abel Wu <wuyun.abel@bytedance.com>, 
	Breno Leitao <leitao@debian.org>, Pavel Begunkov <asml.silence@gmail.com>, David Wei <dw@davidwei.uk>, 
	Jason Gunthorpe <jgg@ziepe.ca>, Shailend Chand <shailend@google.com>, 
	Harshitha Ramamurthy <hramamurthy@google.com>, Shakeel Butt <shakeel.butt@linux.dev>, 
	Jeroen de Borst <jeroendb@google.com>, Praveen Kaligineedi <pkaligineedi@google.com>, 
	Willem de Bruijn <willemb@google.com>
Content-Type: text/plain; charset="UTF-8"

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>

---

v8:
- Rename netdev_dmabuf_binding -> net_devmem_dmabuf_binding to avoid
  patch-by-patch build error.
- Move niov->pp_magic/pp/pp_ref_counter usage to later patch to avoid
  patch-by-patch build error.

v7:
- netdev_ -> net_devmem_* naming (Yunsheng).

v6:
- Add comment on net_iov_dma_addr to explain why we don't use
  niov->dma_addr (Pavel)
- Refactor new functions into net/core/devmem.c (Pavel)

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

---
 include/net/devmem.h | 13 +++++++++++++
 include/net/netmem.h | 40 ++++++++++++++++++++++++++++++++++++++++
 net/core/devmem.c    | 36 ++++++++++++++++++++++++++++++++++++
 3 files changed, 89 insertions(+)

diff --git a/include/net/devmem.h b/include/net/devmem.h
index fa03bdabdffd..cd3186f5d1fb 100644
--- a/include/net/devmem.h
+++ b/include/net/devmem.h
@@ -68,7 +68,20 @@ int net_devmem_bind_dmabuf(struct net_device *dev, unsigned int dmabuf_fd,
 void net_devmem_unbind_dmabuf(struct net_devmem_dmabuf_binding *binding);
 int net_devmem_bind_dmabuf_to_queue(struct net_device *dev, u32 rxq_idx,
 				    struct net_devmem_dmabuf_binding *binding);
+struct net_iov *
+net_devmem_alloc_dmabuf(struct net_devmem_dmabuf_binding *binding);
+void net_devmem_free_dmabuf(struct net_iov *ppiov);
 #else
+static inline struct net_iov *
+net_devmem_alloc_dmabuf(struct net_devmem_dmabuf_binding *binding)
+{
+	return NULL;
+}
+
+static inline void net_devmem_free_dmabuf(struct net_iov *ppiov)
+{
+}
+
 static inline void
 __net_devmem_dmabuf_binding_free(struct net_devmem_dmabuf_binding *binding)
 {
diff --git a/include/net/netmem.h b/include/net/netmem.h
index 72e932a1a948..33014370a885 100644
--- a/include/net/netmem.h
+++ b/include/net/netmem.h
@@ -14,8 +14,48 @@
 
 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;
+}
+
+/* This returns the absolute dma_addr_t calculated from
+ * net_iov_owner(niov)->owner->base_dma_addr, not the page_pool-owned
+ * niov->dma_addr.
+ *
+ * The absolute dma_addr_t is a dma_addr_t that is always uncompressed.
+ *
+ * The page_pool-owner niov->dma_addr is the absolute dma_addr compressed into
+ * an unsigned long. Special handling is done when the unsigned long is 32-bit
+ * but the dma_addr_t is 64-bit.
+ *
+ * In general code looking for the dma_addr_t should use net_iov_dma_addr(),
+ * while page_pool code looking for the unsigned long dma_addr which mirrors
+ * the field in struct page should use niov->dma_addr.
+ */
+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 net_devmem_dmabuf_binding *
+net_iov_binding(const struct net_iov *niov)
+{
+	return net_iov_owner(niov)->binding;
+}
+
 /* netmem */
 
 /**
diff --git a/net/core/devmem.c b/net/core/devmem.c
index 02a6abaecf40..268fc8455a6d 100644
--- a/net/core/devmem.c
+++ b/net/core/devmem.c
@@ -103,6 +103,42 @@ static int net_devmem_restart_rx_queue(struct net_device *dev, int rxq_idx)
 	return err;
 }
 
+struct net_iov *
+net_devmem_alloc_dmabuf(struct net_devmem_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->dma_addr = 0;
+
+	net_devmem_dmabuf_binding_get(binding);
+
+	return niov;
+}
+
+void net_devmem_free_dmabuf(struct net_iov *niov)
+{
+	struct net_devmem_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);
+
+	net_devmem_dmabuf_binding_put(binding);
+}
+
 /* Protected by rtnl_lock() */
 static DEFINE_XARRAY_FLAGS(net_devmem_dmabuf_bindings, XA_FLAGS_ALLOC1);
 
-- 
2.44.0.478.gd926399ef9-goog