netdev - [net-next PATCH V2 3/3] page_pool: use DMA_ATTR_SKIP_CPU

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Date:   Tue, 12 Feb 2019 15:49:13 +0100
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     netdev@...r.kernel.org, linux-mm@...ck.org
Cc:     Toke Høiland-Jørgensen <toke@...e.dk>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        willy@...radead.org, Saeed Mahameed <saeedm@...lanox.com>,
        Alexander Duyck <alexander.duyck@...il.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        mgorman@...hsingularity.net,
        "David S. Miller" <davem@...emloft.net>,
        Tariq Toukan <tariqt@...lanox.com>
Subject: [net-next PATCH V2 3/3] page_pool: use DMA_ATTR_SKIP_CPU_SYNC for
 DMA mappings

As pointed out by Alexander Duyck, the DMA mapping done in page_pool needs
to use the DMA attribute DMA_ATTR_SKIP_CPU_SYNC.

As the principle behind page_pool keeping the pages mapped is that the
driver takes over the DMA-sync steps.

Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>
---
 net/core/page_pool.c |   11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index 897a69a1477e..7e624c2cd709 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -141,9 +141,9 @@ static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool,
 	 * into page private data (i.e 32bit cpu with 64bit DMA caps)
 	 * This mapping is kept for lifetime of page, until leaving pool.
 	 */
-	dma = dma_map_page(pool->p.dev, page, 0,
-			   (PAGE_SIZE << pool->p.order),
-			   pool->p.dma_dir);
+	dma = dma_map_page_attrs(pool->p.dev, page, 0,
+				 (PAGE_SIZE << pool->p.order),
+				 pool->p.dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
 	if (dma_mapping_error(pool->p.dev, dma)) {
 		put_page(page);
 		return NULL;
@@ -184,8 +184,9 @@ static void __page_pool_clean_page(struct page_pool *pool,
 
 	dma = page->dma_addr;
 	/* DMA unmap */
-	dma_unmap_page(pool->p.dev, dma,
-		       PAGE_SIZE << pool->p.order, pool->p.dma_dir);
+	dma_unmap_page_attr(pool->p.dev, dma,
+			    PAGE_SIZE << pool->p.order, pool->p.dma_dir,
+			    DMA_ATTR_SKIP_CPU_SYNC);
 	page->dma_addr = 0;
 }