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Message-ID: <20250222191517.743530-2-almasrymina@google.com>
Date: Sat, 22 Feb 2025 19:15:09 +0000
From: Mina Almasry <almasrymina@...gle.com>
To: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-doc@...r.kernel.org, virtualization@...ts.linux.dev,
kvm@...r.kernel.org, linux-kselftest@...r.kernel.org
Cc: Mina Almasry <almasrymina@...gle.com>, Donald Hunter <donald.hunter@...il.com>,
Jakub Kicinski <kuba@...nel.org>, "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>,
Jonathan Corbet <corbet@....net>, Andrew Lunn <andrew+netdev@...n.ch>,
Jeroen de Borst <jeroendb@...gle.com>, Harshitha Ramamurthy <hramamurthy@...gle.com>,
Kuniyuki Iwashima <kuniyu@...zon.com>, Willem de Bruijn <willemb@...gle.com>, David Ahern <dsahern@...nel.org>,
Neal Cardwell <ncardwell@...gle.com>, Stefan Hajnoczi <stefanha@...hat.com>,
Stefano Garzarella <sgarzare@...hat.com>, "Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>,
Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
"Eugenio Pérez" <eperezma@...hat.com>, Shuah Khan <shuah@...nel.org>, sdf@...ichev.me,
asml.silence@...il.com, dw@...idwei.uk, Jamal Hadi Salim <jhs@...atatu.com>,
Victor Nogueira <victor@...atatu.com>, Pedro Tammela <pctammela@...atatu.com>,
Samiullah Khawaja <skhawaja@...gle.com>
Subject: [PATCH net-next v5 1/9] net: add get_netmem/put_netmem support
Currently net_iovs support only pp ref counts, and do not support a
page ref equivalent.
This is fine for the RX path as net_iovs are used exclusively with the
pp and only pp refcounting is needed there. The TX path however does not
use pp ref counts, thus, support for get_page/put_page equivalent is
needed for netmem.
Support get_netmem/put_netmem. Check the type of the netmem before
passing it to page or net_iov specific code to obtain a page ref
equivalent.
For dmabuf net_iovs, we obtain a ref on the underlying binding. This
ensures the entire binding doesn't disappear until all the net_iovs have
been put_netmem'ed. We do not need to track the refcount of individual
dmabuf net_iovs as we don't allocate/free them from a pool similar to
what the buddy allocator does for pages.
This code is written to be extensible by other net_iov implementers.
get_netmem/put_netmem will check the type of the netmem and route it to
the correct helper:
pages -> [get|put]_page()
dmabuf net_iovs -> net_devmem_[get|put]_net_iov()
new net_iovs -> new helpers
Signed-off-by: Mina Almasry <almasrymina@...gle.com>
Acked-by: Stanislav Fomichev <sdf@...ichev.me>
---
v2:
- Add comment on top of refcount_t ref explaining the usage in the XT
path.
- Fix missing definition of net_devmem_dmabuf_binding_put in this patch.
---
include/linux/skbuff_ref.h | 4 ++--
include/net/netmem.h | 3 +++
net/core/devmem.c | 10 ++++++++++
net/core/devmem.h | 20 ++++++++++++++++++++
net/core/skbuff.c | 30 ++++++++++++++++++++++++++++++
5 files changed, 65 insertions(+), 2 deletions(-)
diff --git a/include/linux/skbuff_ref.h b/include/linux/skbuff_ref.h
index 0f3c58007488..9e49372ef1a0 100644
--- a/include/linux/skbuff_ref.h
+++ b/include/linux/skbuff_ref.h
@@ -17,7 +17,7 @@
*/
static inline void __skb_frag_ref(skb_frag_t *frag)
{
- get_page(skb_frag_page(frag));
+ get_netmem(skb_frag_netmem(frag));
}
/**
@@ -40,7 +40,7 @@ static inline void skb_page_unref(netmem_ref netmem, bool recycle)
if (recycle && napi_pp_put_page(netmem))
return;
#endif
- put_page(netmem_to_page(netmem));
+ put_netmem(netmem);
}
/**
diff --git a/include/net/netmem.h b/include/net/netmem.h
index c61d5b21e7b4..a2148ffb203d 100644
--- a/include/net/netmem.h
+++ b/include/net/netmem.h
@@ -264,4 +264,7 @@ static inline unsigned long netmem_get_dma_addr(netmem_ref netmem)
return __netmem_clear_lsb(netmem)->dma_addr;
}
+void get_netmem(netmem_ref netmem);
+void put_netmem(netmem_ref netmem);
+
#endif /* _NET_NETMEM_H */
diff --git a/net/core/devmem.c b/net/core/devmem.c
index 7c6e0b5b6acb..b1aafc66ebb7 100644
--- a/net/core/devmem.c
+++ b/net/core/devmem.c
@@ -325,6 +325,16 @@ net_devmem_bind_dmabuf(struct net_device *dev, unsigned int dmabuf_fd,
return ERR_PTR(err);
}
+void net_devmem_get_net_iov(struct net_iov *niov)
+{
+ net_devmem_dmabuf_binding_get(net_devmem_iov_binding(niov));
+}
+
+void net_devmem_put_net_iov(struct net_iov *niov)
+{
+ net_devmem_dmabuf_binding_put(net_devmem_iov_binding(niov));
+}
+
/*** "Dmabuf devmem memory provider" ***/
int mp_dmabuf_devmem_init(struct page_pool *pool)
diff --git a/net/core/devmem.h b/net/core/devmem.h
index 7fc158d52729..946f2e015746 100644
--- a/net/core/devmem.h
+++ b/net/core/devmem.h
@@ -29,6 +29,10 @@ struct net_devmem_dmabuf_binding {
* The binding undos itself and unmaps the underlying dmabuf once all
* those refs are dropped and the binding is no longer desired or in
* use.
+ *
+ * net_devmem_get_net_iov() on dmabuf net_iovs will increment this
+ * reference, making sure that the binding remains alive until all the
+ * net_iovs are no longer used.
*/
refcount_t ref;
@@ -111,6 +115,9 @@ net_devmem_dmabuf_binding_put(struct net_devmem_dmabuf_binding *binding)
__net_devmem_dmabuf_binding_free(binding);
}
+void net_devmem_get_net_iov(struct net_iov *niov);
+void net_devmem_put_net_iov(struct net_iov *niov);
+
struct net_iov *
net_devmem_alloc_dmabuf(struct net_devmem_dmabuf_binding *binding);
void net_devmem_free_dmabuf(struct net_iov *ppiov);
@@ -120,6 +127,19 @@ bool net_is_devmem_iov(struct net_iov *niov);
#else
struct net_devmem_dmabuf_binding;
+static inline void
+net_devmem_dmabuf_binding_put(struct net_devmem_dmabuf_binding *binding)
+{
+}
+
+static inline void net_devmem_get_net_iov(struct net_iov *niov)
+{
+}
+
+static inline void net_devmem_put_net_iov(struct net_iov *niov)
+{
+}
+
static inline void
__net_devmem_dmabuf_binding_free(struct net_devmem_dmabuf_binding *binding)
{
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 5b241c9e6f38..6e853d55a3e8 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -89,6 +89,7 @@
#include <linux/textsearch.h>
#include "dev.h"
+#include "devmem.h"
#include "netmem_priv.h"
#include "sock_destructor.h"
@@ -7253,3 +7254,32 @@ bool csum_and_copy_from_iter_full(void *addr, size_t bytes,
return false;
}
EXPORT_SYMBOL(csum_and_copy_from_iter_full);
+
+void get_netmem(netmem_ref netmem)
+{
+ if (netmem_is_net_iov(netmem)) {
+ /* Assume any net_iov is devmem and route it to
+ * net_devmem_get_net_iov. As new net_iov types are added they
+ * need to be checked here.
+ */
+ net_devmem_get_net_iov(netmem_to_net_iov(netmem));
+ return;
+ }
+ get_page(netmem_to_page(netmem));
+}
+EXPORT_SYMBOL(get_netmem);
+
+void put_netmem(netmem_ref netmem)
+{
+ if (netmem_is_net_iov(netmem)) {
+ /* Assume any net_iov is devmem and route it to
+ * net_devmem_put_net_iov. As new net_iov types are added they
+ * need to be checked here.
+ */
+ net_devmem_put_net_iov(netmem_to_net_iov(netmem));
+ return;
+ }
+
+ put_page(netmem_to_page(netmem));
+}
+EXPORT_SYMBOL(put_netmem);
--
2.48.1.601.g30ceb7b040-goog
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