[Linuxarm] Re: [PATCH net] page_pool: Revert "page_pool: disable dma mapping support..."

On Wed, 17 Nov 2021 at 13:48, Jesper Dangaard Brouer jbrouer@redhat.com wrote:

Added CC: linux-mm@kvack.org

On 17/11/2021 08.56, Yunsheng Lin wrote:

...

This reverts commit d00e60ee54b12de945b8493cf18c1ada9e422514.

As reported by Guillaume in [1]: Enabling LPAE always enables CONFIG_ARCH_DMA_ADDR_T_64BIT in 32-bit systems, which breaks the bootup proceess when a ethernet driver is using page pool with PP_FLAG_DMA_MAP flag. As we were hoping we had no active consumers for such system when we removed the dma mapping support, and LPAE seems like a common feature for 32 bits system, so revert it.

1. https://www.spinics.net/lists/netdev/msg779890.html

Fixes: d00e60ee54b1 ("page_pool: disable dma mapping support for 32-bit arch with 64-bit DMA") Signed-off-by: Yunsheng Lin linyunsheng@huawei.com

---

include/linux/mm_types.h | 13 ++++++++++++- include/net/page_pool.h | 12 +++++++++++- net/core/page_pool.c | 10 ++++------ 3 files changed, 27 insertions(+), 8 deletions(-)

Acked-by: Jesper Dangaard Brouer brouer@redhat.com

Too bad that we have to keep this code-uglyness in struct page, and handling in page_pool.

Indeed :(

Acked-by: Ilias Apalodimas ilias.apalodimas@linaro.org

...

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index bb8c6f5f19bc..c3a6e6209600 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -105,7 +105,18 @@ struct page { struct page_pool *pp; unsigned long _pp_mapping_pad; unsigned long dma_addr;

•                 atomic_long_t pp_frag_count;
  

•                 union {
  

•                         /**
  

•                          * dma_addr_upper: might require a 64-bit
  

•                          * value on 32-bit architectures.
  

•                          */
  

•                         unsigned long dma_addr_upper;
  

•                         /**
  

•                          * For frag page support, not supported in
  

•                          * 32-bit architectures with 64-bit DMA.
  

•                          */
  

•                         atomic_long_t pp_frag_count;
  

•                 };
          };
          struct {        /* slab, slob and slub */
                  union {
  

diff --git a/include/net/page_pool.h b/include/net/page_pool.h index 3855f069627f..a4082406a003 100644 --- a/include/net/page_pool.h +++ b/include/net/page_pool.h @@ -216,14 +216,24 @@ static inline void page_pool_recycle_direct(struct page_pool *pool, page_pool_put_full_page(pool, page, true); }

+#define PAGE_POOL_DMA_USE_PP_FRAG_COUNT \

•         (sizeof(dma_addr_t) > sizeof(unsigned long))
  

• static inline dma_addr_t page_pool_get_dma_addr(struct page *page) {

• return page->dma_addr;
  

• dma_addr_t ret = page->dma_addr;
  

• if (PAGE_POOL_DMA_USE_PP_FRAG_COUNT)
  

•         ret |= (dma_addr_t)page->dma_addr_upper << 16 << 16;
  

• return ret;
  

  }

  static inline void page_pool_set_dma_addr(struct page *page, dma_addr_t addr) { page->dma_addr = addr;

• if (PAGE_POOL_DMA_USE_PP_FRAG_COUNT)
  

•         page->dma_addr_upper = upper_32_bits(addr);
  

  }

  static inline void page_pool_set_frag_count(struct page *page, long nr)

diff --git a/net/core/page_pool.c b/net/core/page_pool.c index 9b60e4301a44..1a6978427d6c 100644 --- a/net/core/page_pool.c +++ b/net/core/page_pool.c @@ -49,12 +49,6 @@ static int page_pool_init(struct page_pool *pool, * which is the XDP_TX use-case. */ if (pool->p.flags & PP_FLAG_DMA_MAP) {

•         /* DMA-mapping is not supported on 32-bit systems with
  

•          * 64-bit DMA mapping.
  

•          */
  

•         if (sizeof(dma_addr_t) > sizeof(unsigned long))
  

•                 return -EOPNOTSUPP;
  

•         if ((pool->p.dma_dir != DMA_FROM_DEVICE) &&
              (pool->p.dma_dir != DMA_BIDIRECTIONAL))
                  return -EINVAL;
  

@@ -75,6 +69,10 @@ static int page_pool_init(struct page_pool *pool, */ }

• if (PAGE_POOL_DMA_USE_PP_FRAG_COUNT &&
  

•     pool->p.flags & PP_FLAG_PAGE_FRAG)
  

•         return -EINVAL;
  

• if (ptr_ring_init(&pool->ring, ring_qsize, GFP_KERNEL) < 0)
          return -ENOMEM;