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Date: Mon,  4 Mar 2024 18:01:41 -0800
From: Mina Almasry <almasrymina@...gle.com>
To: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-doc@...r.kernel.org, linux-alpha@...r.kernel.org, 
	linux-mips@...r.kernel.org, linux-parisc@...r.kernel.org, 
	sparclinux@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
	linux-arch@...r.kernel.org, bpf@...r.kernel.org, 
	linux-kselftest@...r.kernel.org, linux-media@...r.kernel.org, 
	dri-devel@...ts.freedesktop.org
Cc: Mina Almasry <almasrymina@...gle.com>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Jonathan Corbet <corbet@....net>, Richard Henderson <richard.henderson@...aro.org>, 
	Ivan Kokshaysky <ink@...assic.park.msu.ru>, Matt Turner <mattst88@...il.com>, 
	Thomas Bogendoerfer <tsbogend@...ha.franken.de>, 
	"James E.J. Bottomley" <James.Bottomley@...senPartnership.com>, Helge Deller <deller@....de>, 
	Andreas Larsson <andreas@...sler.com>, Jesper Dangaard Brouer <hawk@...nel.org>, 
	Ilias Apalodimas <ilias.apalodimas@...aro.org>, Steven Rostedt <rostedt@...dmis.org>, 
	Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, 
	Arnd Bergmann <arnd@...db.de>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, 
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>, 
	Jiri Olsa <jolsa@...nel.org>, David Ahern <dsahern@...nel.org>, 
	Willem de Bruijn <willemdebruijn.kernel@...il.com>, Shuah Khan <shuah@...nel.org>, 
	Sumit Semwal <sumit.semwal@...aro.org>, 
	"Christian König" <christian.koenig@....com>, Pavel Begunkov <asml.silence@...il.com>, 
	David Wei <dw@...idwei.uk>, Jason Gunthorpe <jgg@...pe.ca>, Yunsheng Lin <linyunsheng@...wei.com>, 
	Shailend Chand <shailend@...gle.com>, Harshitha Ramamurthy <hramamurthy@...gle.com>, 
	Shakeel Butt <shakeelb@...gle.com>, Jeroen de Borst <jeroendb@...gle.com>, 
	Praveen Kaligineedi <pkaligineedi@...gle.com>, Willem de Bruijn <willemb@...gle.com>, 
	Kaiyuan Zhang <kaiyuanz@...gle.com>
Subject: [RFC PATCH net-next v6 06/15] netdev: netdevice devmem allocator

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@...gle.com>
Signed-off-by: Kaiyuan Zhang <kaiyuanz@...gle.com>
Signed-off-by: Mina Almasry <almasrymina@...gle.com>

---

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 | 12 ++++++++++++
 include/net/netmem.h | 40 ++++++++++++++++++++++++++++++++++++++++
 net/core/devmem.c    | 38 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 90 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 72e932a1a948..ca17ea1d33f8 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 netdev_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 779ad990971e..57d3a1f223ef 100644
--- a/net/core/devmem.c
+++ b/net/core/devmem.c
@@ -93,6 +93,44 @@ 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);
 
-- 
2.44.0.rc1.240.g4c46232300-goog


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