[PATCH net-next v14 07/13] memory-provider: dmabuf devmem memory provider

Mina Almasry
2024-06-25T19:54:25Z

Implement a memory provider that allocates dmabuf devmem in the form of
net_iov.

The provider receives a reference to the struct netdev_dmabuf_binding
via the pool->mp_priv pointer. The driver needs to set this pointer for
the provider in the net_iov.

The provider obtains a reference on the netdev_dmabuf_binding which
guarantees the binding and the underlying mapping remains alive until
the provider is destroyed.

Usage of PP_FLAG_DMA_MAP is required for this memory provide such that
the page_pool can provide the driver with the dma-addrs of the devmem.

Support for PP_FLAG_DMA_SYNC_DEV is omitted for simplicity & p.order !=
0.

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>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>

---

v13:
- Return on warning (Pavel).
- Fixed pool->recycle_stats not being freed on error (Pavel).
- Applied reviewed-by from Pavel.

v11:
- Rebase to not use the ops. (Christoph)

v8:
- Use skb_frag_size instead of frag->bv_len to fix patch-by-patch build
error

v6:
- refactor new memory provider functions into net/core/devmem.c (Pavel)

v2:
- Disable devmem for p.order != 0

v1:
- static_branch check in page_is_page_pool_iov() (Willem & Paolo).
- PP_DEVMEM -> PP_IOV (David).
- Require PP_FLAG_DMA_MAP (Jakub).

---
include/net/mp_dmabuf_devmem.h | 44 +++++++++++++++++++
include/net/netmem.h | 15 +++++++
include/net/page_pool/helpers.h | 22 ++++++++++
include/net/page_pool/types.h | 2 +
net/core/devmem.c | 77 +++++++++++++++++++++++++++++++++
net/core/page_pool.c | 74 ++++++++++++++++++++-----------
6 files changed, 208 insertions(+), 26 deletions(-)
create mode 100644 include/net/mp_dmabuf_devmem.h

diff --git a/include/net/mp_dmabuf_devmem.h b/include/net/mp_dmabuf_devmem.h
new file mode 100644
index 0000000000000..300a2356eed00
--- /dev/null
+++ b/include/net/mp_dmabuf_devmem.h
@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Dmabuf device memory provider.
+ *
+ * Authors: Mina Almasry <almasrymina@google.com>
+ *
+ */
+#ifndef _NET_MP_DMABUF_DEVMEM_H
+#define _NET_MP_DMABUF_DEVMEM_H
+
+#include <net/netmem.h>
+
+#if defined(CONFIG_DMA_SHARED_BUFFER) && defined(CONFIG_GENERIC_ALLOCATOR)
+int mp_dmabuf_devmem_init(struct page_pool *pool);
+
+netmem_ref mp_dmabuf_devmem_alloc_netmems(struct page_pool *pool, gfp_t gfp);
+
+void mp_dmabuf_devmem_destroy(struct page_pool *pool);
+
+bool mp_dmabuf_devmem_release_page(struct page_pool *pool, netmem_ref netmem);
+#else
+static inline int mp_dmabuf_devmem_init(struct page_pool *pool)
+{
+ return -EOPNOTSUPP;
+}
+
+static inline netmem_ref mp_dmabuf_devmem_alloc_netmems(struct page_pool *pool,
+ gfp_t gfp)
+{
+ return 0;
+}
+
+static inline void mp_dmabuf_devmem_destroy(struct page_pool *pool)
+{
+}
+
+static inline bool mp_dmabuf_devmem_release_page(struct page_pool *pool,
+ netmem_ref netmem)
+{
+ return false;
+}
+#endif
+
+#endif /* _NET_MP_DMABUF_DEVMEM_H */
diff --git a/include/net/netmem.h b/include/net/netmem.h
index 35ad237fdf29e..7c28d6fac6242 100644
--- a/include/net/netmem.h
+++ b/include/net/netmem.h
@@ -100,6 +100,21 @@ static inline struct page *netmem_to_page(netmem_ref netmem)
return (__force struct page *)netmem;
}

+static inline struct net_iov *netmem_to_net_iov(netmem_ref netmem)
+{
+ if (netmem_is_net_iov(netmem))
+ return (struct net_iov *)((__force unsigned long)netmem &
+ ~NET_IOV);
+
+ DEBUG_NET_WARN_ON_ONCE(true);
+ return NULL;
+}
+
+static inline netmem_ref net_iov_to_netmem(struct net_iov *niov)
+{
+ return (__force netmem_ref)((unsigned long)niov | NET_IOV);
+}
+
static inline netmem_ref page_to_netmem(struct page *page)
{
return (__force netmem_ref)page;
diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h
index 0c95594ce8e1c..8058cb13e695c 100644
--- a/include/net/page_pool/helpers.h
+++ b/include/net/page_pool/helpers.h
@@ -476,4 +476,26 @@ static inline void page_pool_nid_changed(struct page_pool *pool, int new_nid)
page_pool_update_nid(pool, new_nid);
}

+static inline void page_pool_set_pp_info(struct page_pool *pool,
+ netmem_ref netmem)
+{
+ netmem_set_pp(netmem, pool);
+ netmem_or_pp_magic(netmem, PP_SIGNATURE);
+
+ /* Ensuring all pages have been split into one fragment initially:
+ * page_pool_set_pp_info() is only called once for every page when it
+ * is allocated from the page allocator and page_pool_fragment_page()
+ * is dirtying the same cache line as the page->pp_magic above, so
+ * the overhead is negligible.
+ */
+ page_pool_fragment_netmem(netmem, 1);
+ if (pool->has_init_callback)
+ pool->slow.init_callback(netmem, pool->slow.init_arg);
+}
+
+static inline void page_pool_clear_pp_info(netmem_ref netmem)
+{
+ netmem_clear_pp_magic(netmem);
+ netmem_set_pp(netmem, NULL);
+}
#endif /* _NET_PAGE_POOL_HELPERS_H */
diff --git a/include/net/page_pool/types.h b/include/net/page_pool/types.h
index 0693117f8d74f..2179a55f21448 100644
--- a/include/net/page_pool/types.h
+++ b/include/net/page_pool/types.h
@@ -52,6 +52,7 @@ struct pp_alloc_cache {
* @nid: NUMA node id to allocate from pages from
* @dev: device, for DMA pre-mapping purposes
* @napi: NAPI which is the sole consumer of pages, otherwise NULL
+ * @queue: struct netdev_rx_queue this page_pool is being created for.
* @dma_dir: DMA mapping direction
* @max_len: max DMA sync memory size for PP_FLAG_DMA_SYNC_DEV
* @offset: DMA sync address offset for PP_FLAG_DMA_SYNC_DEV
@@ -66,6 +67,7 @@ struct page_pool_params {
int nid;
struct device *dev;
struct napi_struct *napi;
+ struct netdev_rx_queue *queue;
enum dma_data_direction dma_dir;
unsigned int max_len;
unsigned int offset;
diff --git a/net/core/devmem.c b/net/core/devmem.c
index 0da3295188f68..7afaf17801ef6 100644
--- a/net/core/devmem.c
+++ b/net/core/devmem.c
@@ -17,6 +17,7 @@
#include <linux/genalloc.h>
#include <linux/dma-buf.h>
#include <net/devmem.h>
+#include <net/mp_dmabuf_devmem.h>
#include <net/netdev_queues.h>

/* Device memory support */
@@ -296,4 +297,80 @@ int net_devmem_bind_dmabuf(struct net_device *dev, unsigned int dmabuf_fd,
dma_buf_put(dmabuf);
return err;
}
+
+/*** "Dmabuf devmem memory provider" ***/
+
+int mp_dmabuf_devmem_init(struct page_pool *pool)
+{
+ struct net_devmem_dmabuf_binding *binding = pool->mp_priv;
+
+ if (!binding)
+ return -EINVAL;
+
+ if (!pool->dma_map)
+ return -EOPNOTSUPP;
+
+ if (pool->dma_sync)
+ return -EOPNOTSUPP;
+
+ if (pool->p.order != 0)
+ return -E2BIG;
+
+ net_devmem_dmabuf_binding_get(binding);
+ return 0;
+}
+
+netmem_ref mp_dmabuf_devmem_alloc_netmems(struct page_pool *pool, gfp_t gfp)
+{
+ struct net_devmem_dmabuf_binding *binding = pool->mp_priv;
+ netmem_ref netmem;
+ struct net_iov *niov;
+ dma_addr_t dma_addr;
+
+ niov = net_devmem_alloc_dmabuf(binding);
+ if (!niov)
+ return 0;
+
+ dma_addr = net_devmem_get_dma_addr(niov);
+
+ netmem = net_iov_to_netmem(niov);
+
+ page_pool_set_pp_info(pool, netmem);
+
+ if (page_pool_set_dma_addr_netmem(netmem, dma_addr))
+ goto err_free;
+
+ pool->pages_state_hold_cnt++;
+ trace_page_pool_state_hold(pool, netmem, pool->pages_state_hold_cnt);
+ return netmem;
+
+err_free:
+ net_devmem_free_dmabuf(niov);
+ return 0;
+}
+
+void mp_dmabuf_devmem_destroy(struct page_pool *pool)
+{
+ struct net_devmem_dmabuf_binding *binding = pool->mp_priv;
+
+ net_devmem_dmabuf_binding_put(binding);
+}
+
+bool mp_dmabuf_devmem_release_page(struct page_pool *pool, netmem_ref netmem)
+{
+ if (WARN_ON_ONCE(!netmem_is_net_iov(netmem)))
+ return false;
+
+ if (WARN_ON_ONCE(atomic_long_read(netmem_get_pp_ref_count_ref(netmem)) !=
+ 1))
+ return false;
+
+ page_pool_clear_pp_info(netmem);
+
+ net_devmem_free_dmabuf(netmem_to_net_iov(netmem));
+
+ /* We don't want the page pool put_page()ing our net_iovs. */
+ return false;
+}
+
#endif
diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index e65476e9956f3..234973c9bed0d 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -13,6 +13,7 @@

#include <net/page_pool/helpers.h>
#include <net/xdp.h>
+#include <net/netdev_rx_queue.h>

#include <linux/dma-direction.h>
#include <linux/dma-mapping.h>
@@ -21,12 +22,16 @@
#include <linux/poison.h>
#include <linux/ethtool.h>
#include <linux/netdevice.h>
+#include <linux/genalloc.h>
+#include <net/devmem.h>
+#include <net/mp_dmabuf_devmem.h>

#include <trace/events/page_pool.h>

#include "page_pool_priv.h"

DEFINE_STATIC_KEY_FALSE(page_pool_mem_providers);
+EXPORT_SYMBOL(page_pool_mem_providers);

#define DEFER_TIME (msecs_to_jiffies(1000))
#define DEFER_WARN_INTERVAL (60 * HZ)
@@ -188,6 +193,7 @@ static int page_pool_init(struct page_pool *pool,
int cpuid)
{
unsigned int ring_qsize = 1024; /* Default */
+ int err;

page_pool_struct_check();

@@ -269,7 +275,29 @@ static int page_pool_init(struct page_pool *pool,
if (pool->dma_map)
get_device(pool->p.dev);

+ if (pool->p.queue)
+ pool->mp_priv = READ_ONCE(pool->p.queue->mp_params.mp_priv);
+
+ if (pool->mp_priv) {
+ err = mp_dmabuf_devmem_init(pool);
+ if (err) {
+ pr_warn("%s() mem-provider init failed %d\n", __func__,
+ err);
+ goto free_ptr_ring;
+ }
+
+ static_branch_inc(&page_pool_mem_providers);
+ }
+
return 0;
+
+free_ptr_ring:
+ ptr_ring_cleanup(&pool->ring, NULL);
+#ifdef CONFIG_PAGE_POOL_STATS
+ if (!pool->system)
+ free_percpu(pool->recycle_stats);
+#endif
+ return err;
}

static void page_pool_uninit(struct page_pool *pool)
@@ -453,28 +481,6 @@ static bool page_pool_dma_map(struct page_pool *pool, netmem_ref netmem)
return false;
}

-static void page_pool_set_pp_info(struct page_pool *pool, netmem_ref netmem)
-{
- netmem_set_pp(netmem, pool);
- netmem_or_pp_magic(netmem, PP_SIGNATURE);
-
- /* Ensuring all pages have been split into one fragment initially:
- * page_pool_set_pp_info() is only called once for every page when it
- * is allocated from the page allocator and page_pool_fragment_page()
- * is dirtying the same cache line as the page->pp_magic above, so
- * the overhead is negligible.
- */
- page_pool_fragment_netmem(netmem, 1);
- if (pool->has_init_callback)
- pool->slow.init_callback(netmem, pool->slow.init_arg);
-}
-
-static void page_pool_clear_pp_info(netmem_ref netmem)
-{
- netmem_clear_pp_magic(netmem);
- netmem_set_pp(netmem, NULL);
-}
-
static struct page *__page_pool_alloc_page_order(struct page_pool *pool,
gfp_t gfp)
{
@@ -570,7 +576,10 @@ netmem_ref page_pool_alloc_netmem(struct page_pool *pool, gfp_t gfp)
return netmem;

/* Slow-path: cache empty, do real allocation */
- netmem = __page_pool_alloc_pages_slow(pool, gfp);
+ if (static_branch_unlikely(&page_pool_mem_providers) && pool->mp_priv)
+ netmem = mp_dmabuf_devmem_alloc_netmems(pool, gfp);
+ else
+ netmem = __page_pool_alloc_pages_slow(pool, gfp);
return netmem;
}
EXPORT_SYMBOL(page_pool_alloc_netmem);
@@ -634,8 +643,13 @@ static __always_inline void __page_pool_release_page_dma(struct page_pool *pool,
void page_pool_return_page(struct page_pool *pool, netmem_ref netmem)
{
int count;
+ bool put;

- __page_pool_release_page_dma(pool, netmem);
+ put = true;
+ if (static_branch_unlikely(&page_pool_mem_providers) && pool->mp_priv)
+ put = mp_dmabuf_devmem_release_page(pool, netmem);
+ else
+ __page_pool_release_page_dma(pool, netmem);

/* This may be the last page returned, releasing the pool, so
* it is not safe to reference pool afterwards.
@@ -643,8 +657,10 @@ void page_pool_return_page(struct page_pool *pool, netmem_ref netmem)
count = atomic_inc_return_relaxed(&pool->pages_state_release_cnt);
trace_page_pool_state_release(pool, netmem, count);

- page_pool_clear_pp_info(netmem);
- put_page(netmem_to_page(netmem));
+ if (put) {
+ page_pool_clear_pp_info(netmem);
+ put_page(netmem_to_page(netmem));
+ }
/* An optimization would be to call __free_pages(page, pool->p.order)
* knowing page is not part of page-cache (thus avoiding a
* __page_cache_release() call).
@@ -963,6 +979,12 @@ static void __page_pool_destroy(struct page_pool *pool)

page_pool_unlist(pool);
page_pool_uninit(pool);
+
+ if (pool->mp_priv) {
+ mp_dmabuf_devmem_destroy(pool);
+ static_branch_dec(&page_pool_mem_providers);
+ }
+
kfree(pool);