From c25fff7171bebb76243ccc77f0f04aafa3db87be Mon Sep 17 00:00:00 2001 From: Jesper Dangaard Brouer Date: Wed, 13 Feb 2019 02:55:40 +0100 Subject: [PATCH 1/3] mm: add dma_addr_t to struct page The page_pool API is using page->private to store DMA addresses. As pointed out by David Miller we can't use that on 32-bit architectures with 64-bit DMA This patch adds a new dma_addr_t struct to allow storing DMA addresses Signed-off-by: Jesper Dangaard Brouer Signed-off-by: Ilias Apalodimas Acked-by: Andrew Morton Signed-off-by: David S. Miller --- include/linux/mm_types.h | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 2c471a2c43fa..0a36a22228e7 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -95,6 +95,13 @@ struct page { */ unsigned long private; }; + struct { /* page_pool used by netstack */ + /** + * @dma_addr: might require a 64-bit value even on + * 32-bit architectures. + */ + dma_addr_t dma_addr; + }; struct { /* slab, slob and slub */ union { struct list_head slab_list; /* uses lru */ From 1567b85eb8ad2d0fe8d77e50118e876df565d9c7 Mon Sep 17 00:00:00 2001 From: Ilias Apalodimas Date: Wed, 13 Feb 2019 02:55:45 +0100 Subject: [PATCH 2/3] net: page_pool: don't use page->private to store dma_addr_t As pointed out by David Miller the current page_pool implementation stores dma_addr_t in page->private. This won't work on 32-bit platforms with 64-bit DMA addresses since the page->private is an unsigned long and the dma_addr_t a u64. A previous patch is adding dma_addr_t on struct page to accommodate this. This patch adapts the page_pool related functions to use the newly added struct for storing and retrieving DMA addresses from network drivers. Signed-off-by: Ilias Apalodimas Signed-off-by: Jesper Dangaard Brouer Signed-off-by: David S. Miller --- net/core/page_pool.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/net/core/page_pool.c b/net/core/page_pool.c index 43a932cb609b..897a69a1477e 100644 --- a/net/core/page_pool.c +++ b/net/core/page_pool.c @@ -136,7 +136,9 @@ static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool, if (!(pool->p.flags & PP_FLAG_DMA_MAP)) goto skip_dma_map; - /* Setup DMA mapping: use page->private for DMA-addr + /* Setup DMA mapping: use 'struct page' area for storing DMA-addr + * since dma_addr_t can be either 32 or 64 bits and does not always fit + * 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, @@ -146,7 +148,7 @@ static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool, put_page(page); return NULL; } - set_page_private(page, dma); /* page->private = dma; */ + page->dma_addr = dma; skip_dma_map: /* When page just alloc'ed is should/must have refcnt 1. */ @@ -175,13 +177,16 @@ EXPORT_SYMBOL(page_pool_alloc_pages); static void __page_pool_clean_page(struct page_pool *pool, struct page *page) { + dma_addr_t dma; + if (!(pool->p.flags & PP_FLAG_DMA_MAP)) return; + dma = page->dma_addr; /* DMA unmap */ - dma_unmap_page(pool->p.dev, page_private(page), + dma_unmap_page(pool->p.dev, dma, PAGE_SIZE << pool->p.order, pool->p.dma_dir); - set_page_private(page, 0); + page->dma_addr = 0; } /* Return a page to the page allocator, cleaning up our state */ From 13f16d9d4ab7fccc918aafb146ea043be9574d49 Mon Sep 17 00:00:00 2001 From: Jesper Dangaard Brouer Date: Wed, 13 Feb 2019 02:55:50 +0100 Subject: [PATCH 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. Reported-by: Alexander Duyck Signed-off-by: Jesper Dangaard Brouer Signed-off-by: Ilias Apalodimas Signed-off-by: David S. Miller --- 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..5b2252c6d49b 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_attrs(pool->p.dev, dma, + PAGE_SIZE << pool->p.order, pool->p.dma_dir, + DMA_ATTR_SKIP_CPU_SYNC); page->dma_addr = 0; }