Implement a memory provider that allocates dmabuf devmem page_pool_iovs.

Support of PP_FLAG_DMA_MAP, PP_FLAG_DMA_SYNC_DEV, and PP_FLAG_PAGE_FRAG
is omitted. PP_FLAG_DMA_MAP is irrelevant as dma-buf devmem is already
mapped. The other flags are omitted for simplicity.

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 page_pool_params.

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.

Signed-off-by: Willem de Bruijn <will...@google.com>
Signed-off-by: Kaiyuan Zhang <kaiyu...@google.com>

Signed-off-by: Mina Almasry <almasrym...@google.com>
---
 include/net/page_pool.h | 58 ++++++++++++++++++++++++++++++
 net/core/page_pool.c    | 79 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 137 insertions(+)

diff --git a/include/net/page_pool.h b/include/net/page_pool.h
index e395f82e182b..537eb36115ed 100644
--- a/include/net/page_pool.h
+++ b/include/net/page_pool.h
@@ -32,6 +32,7 @@
 #include <linux/mm.h> /* Needed by ptr_ring */
 #include <linux/ptr_ring.h>
 #include <linux/dma-direction.h>
+#include <net/net_debug.h>

 #define PP_FLAG_DMA_MAP                BIT(0) /* Should page_pool do the DMA
                                        * map/unmap
@@ -157,6 +158,7 @@ enum pp_memory_provider_type {
        PP_MP_HUGE_SPLIT, /* 2MB, online page alloc */
        PP_MP_HUGE, /* 2MB, all memory pre-allocated */
        PP_MP_HUGE_1G, /* 1G pages, MEP, pre-allocated */
+       PP_MP_DMABUF_DEVMEM, /* dmabuf devmem provider */
 };

 struct pp_memory_provider_ops {
@@ -170,9 +172,15 @@ extern const struct pp_memory_provider_ops basic_ops;
 extern const struct pp_memory_provider_ops hugesp_ops;
 extern const struct pp_memory_provider_ops huge_ops;
 extern const struct pp_memory_provider_ops huge_1g_ops;
+extern const struct pp_memory_provider_ops dmabuf_devmem_ops;

 /* page_pool_iov support */

+/*  We overload the LSB of the struct page pointer to indicate whether it's
+ *  a page or page_pool_iov.
+ */
+#define PP_DEVMEM 0x01UL
+
 /* Owner of the dma-buf chunks inserted into the gen pool. Each scatterlist
  * entry from the dmabuf is inserted into the genpool as a chunk, and needs
  * this owner struct to keep track of some metadata necessary to create
@@ -196,6 +204,8 @@ struct page_pool_iov {
        struct dmabuf_genpool_chunk_owner *owner;

        refcount_t refcount;
+
+       struct page_pool *pp;
 };

 static inline struct dmabuf_genpool_chunk_owner *
@@ -218,12 +228,60 @@ page_pool_iov_dma_addr(const struct page_pool_iov *ppiov)
               ((dma_addr_t)page_pool_iov_idx(ppiov) << PAGE_SHIFT);
 }

+static inline unsigned long
+page_pool_iov_virtual_addr(const struct page_pool_iov *ppiov)
+{
+       struct dmabuf_genpool_chunk_owner *owner = page_pool_iov_owner(ppiov);
+
+       return owner->base_virtual +
+              ((unsigned long)page_pool_iov_idx(ppiov) << PAGE_SHIFT);
+}
+
 static inline struct netdev_dmabuf_binding *
 page_pool_iov_binding(const struct page_pool_iov *ppiov)
 {
        return page_pool_iov_owner(ppiov)->binding;
 }

+static inline int page_pool_iov_refcount(const struct page_pool_iov *ppiov)
+{
+       return refcount_read(&ppiov->refcount);
+}
+
+static inline void page_pool_iov_get_many(struct page_pool_iov *ppiov,
+                                         unsigned int count)
+{
+       refcount_add(count, &ppiov->refcount);
+}
+
+void __page_pool_iov_free(struct page_pool_iov *ppiov);
+
+static inline void page_pool_iov_put_many(struct page_pool_iov *ppiov,
+                                         unsigned int count)
+{
+       if (!refcount_sub_and_test(count, &ppiov->refcount))
+               return;
+
+       __page_pool_iov_free(ppiov);
+}
+
+/* page pool mm helpers */
+
+static inline bool page_is_page_pool_iov(const struct page *page)
+{
+       return (unsigned long)page & PP_DEVMEM;
+}
+
+static inline struct page_pool_iov *page_to_page_pool_iov(struct page *page)
+{
+       if (page_is_page_pool_iov(page))
+               return (struct page_pool_iov *)((unsigned long)page &
+                                               ~PP_DEVMEM);
+
+       DEBUG_NET_WARN_ON_ONCE(true);
+       return NULL;
+}
+
 struct page_pool {
        struct page_pool_params p;

diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index df3f431fcff3..0a7c08d748b8 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -20,6 +20,7 @@
 #include <linux/poison.h>
 #include <linux/ethtool.h>
 #include <linux/netdevice.h>
+#include <linux/genalloc.h>

 #include <trace/events/page_pool.h>

@@ -236,6 +237,9 @@ static int page_pool_init(struct page_pool *pool,
        case PP_MP_HUGE_1G:
                pool->mp_ops = &huge_1g_ops;
                break;
+       case PP_MP_DMABUF_DEVMEM:
+               pool->mp_ops = &dmabuf_devmem_ops;
+               break;
        default:
                err = -EINVAL;
                goto free_ptr_ring;
@@ -1006,6 +1010,15 @@ bool page_pool_return_skb_page(struct page *page, bool 
napi_safe)
 }
 EXPORT_SYMBOL(page_pool_return_skb_page);

+void __page_pool_iov_free(struct page_pool_iov *ppiov)
+{
+       if (ppiov->pp->mp_ops != &dmabuf_devmem_ops)
+               return;
+
+       netdev_free_devmem(ppiov);
+}
+EXPORT_SYMBOL_GPL(__page_pool_iov_free);
+
 /***********************
  *  Mem provider hack  *
  ***********************/
@@ -1538,3 +1551,69 @@ const struct pp_memory_provider_ops huge_1g_ops = {
        .alloc_pages            = mp_huge_1g_alloc_pages,
        .release_page           = mp_huge_1g_release,
 };
+
+/*** "Dmabuf devmem memory provider" ***/
+
+static int mp_dmabuf_devmem_init(struct page_pool *pool)
+{
+       struct netdev_dmabuf_binding *binding = pool->mp_priv;
+
+       if (!binding)
+               return -EINVAL;
+
+       if (pool->p.flags & PP_FLAG_DMA_MAP ||
+           pool->p.flags & PP_FLAG_DMA_SYNC_DEV ||
+           pool->p.flags & PP_FLAG_PAGE_FRAG)
+               return -EOPNOTSUPP;
+
+       netdev_devmem_binding_get(binding);
+       return 0;
+}
+
+static struct page *mp_dmabuf_devmem_alloc_pages(struct page_pool *pool,
+                                                gfp_t gfp)
+{
+       struct netdev_dmabuf_binding *binding = pool->mp_priv;
+       struct page_pool_iov *ppiov;
+
+       ppiov = netdev_alloc_devmem(binding);
+       if (!ppiov)
+               return NULL;
+
+       ppiov->pp = pool;
+       pool->pages_state_hold_cnt++;
+       trace_page_pool_state_hold(pool, (struct page *)ppiov,
+                                  pool->pages_state_hold_cnt);
+       ppiov = (struct page_pool_iov *)((unsigned long)ppiov | PP_DEVMEM);
+
+       return (struct page *)ppiov;
+}
+
+static void mp_dmabuf_devmem_destroy(struct page_pool *pool)
+{
+       struct netdev_dmabuf_binding *binding = pool->mp_priv;
+
+       netdev_devmem_binding_put(binding);
+}
+
+static bool mp_dmabuf_devmem_release_page(struct page_pool *pool,
+                                         struct page *page)
+{
+       struct page_pool_iov *ppiov;
+
+       if (WARN_ON_ONCE(!page_is_page_pool_iov(page)))
+               return false;
+
+       ppiov = page_to_page_pool_iov(page);
+       page_pool_iov_put_many(ppiov, 1);
+       /* We don't want the page pool put_page()ing our page_pool_iovs. */
+       return false;
+}
+
+const struct pp_memory_provider_ops dmabuf_devmem_ops = {
+       .init                   = mp_dmabuf_devmem_init,
+       .destroy                = mp_dmabuf_devmem_destroy,
+       .alloc_pages            = mp_dmabuf_devmem_alloc_pages,
+       .release_page           = mp_dmabuf_devmem_release_page,
+};
+EXPORT_SYMBOL(dmabuf_devmem_ops);
--
2.41.0.640.ga95def55d0-goog

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