netdev - [PATCH net-next v1 4/7] page_pool: disable sync for cpu for dmabuf memory provider

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Message-ID: <20241029204541.1301203-5-almasrymina@google.com>
Date: Tue, 29 Oct 2024 20:45:38 +0000
From: Mina Almasry <almasrymina@...gle.com>
To: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-kselftest@...r.kernel.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>, 
	Simon Horman <horms@...nel.org>, Jesper Dangaard Brouer <hawk@...nel.org>, 
	Ilias Apalodimas <ilias.apalodimas@...aro.org>, Shuah Khan <shuah@...nel.org>, 
	Jason Gunthorpe <jgg@...pe.ca>
Subject: [PATCH net-next v1 4/7] page_pool: disable sync for cpu for dmabuf
 memory provider

dmabuf dma-addresses should not be dma_sync'd for CPU/device. Typically
its the driver responsibility to dma_sync for CPU, but the driver should
not dma_sync for CPU if the netmem is actually coming from a dmabuf
memory provider.

The page_pool already exposes a helper for dma_sync_for_cpu:
page_pool_dma_sync_for_cpu. Upgrade this existing helper to handle
netmem, and have it skip dma_sync if the memory is from a dmabuf memory
provider. Drivers should migrate to using this helper when adding
support for netmem.

Cc: Jason Gunthorpe <jgg@...pe.ca>
Signed-off-by: Mina Almasry <almasrymina@...gle.com>

---
 include/net/page_pool/helpers.h | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h
index 8e548ff3044c..ad4fed4a791c 100644
--- a/include/net/page_pool/helpers.h
+++ b/include/net/page_pool/helpers.h
@@ -429,9 +429,10 @@ static inline dma_addr_t page_pool_get_dma_addr(const struct page *page)
 }
 
 /**
- * page_pool_dma_sync_for_cpu - sync Rx page for CPU after it's written by HW
+ * page_pool_dma_sync_netmem_for_cpu - sync Rx page for CPU after it's written
+ *				       by HW
  * @pool: &page_pool the @page belongs to
- * @page: page to sync
+ * @netmem: netmem to sync
  * @offset: offset from page start to "hard" start if using PP frags
  * @dma_sync_size: size of the data written to the page
  *
@@ -440,16 +441,28 @@ static inline dma_addr_t page_pool_get_dma_addr(const struct page *page)
  * Note that this version performs DMA sync unconditionally, even if the
  * associated PP doesn't perform sync-for-device.
  */
-static inline void page_pool_dma_sync_for_cpu(const struct page_pool *pool,
-					      const struct page *page,
-					      u32 offset, u32 dma_sync_size)
+static inline void
+page_pool_dma_sync_netmem_for_cpu(const struct page_pool *pool,
+				  const netmem_ref netmem, u32 offset,
+				  u32 dma_sync_size)
 {
+	if (pool->mp_priv)
+		return;
+
 	dma_sync_single_range_for_cpu(pool->p.dev,
-				      page_pool_get_dma_addr(page),
+				      page_pool_get_dma_addr_netmem(netmem),
 				      offset + pool->p.offset, dma_sync_size,
 				      page_pool_get_dma_dir(pool));
 }
 
+static inline void page_pool_dma_sync_for_cpu(const struct page_pool *pool,
+					      struct page *page, u32 offset,
+					      u32 dma_sync_size)
+{
+	page_pool_dma_sync_netmem_for_cpu(pool, page_to_netmem(page), offset,
+					  dma_sync_size);
+}
+
 static inline bool page_pool_put(struct page_pool *pool)
 {
 	return refcount_dec_and_test(&pool->user_cnt);
-- 
2.47.0.163.g1226f6d8fa-goog