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authorYunsheng Lin <linyunsheng@huawei.com>2023-10-13 09:48:21 +0300
committerJakub Kicinski <kuba@kernel.org>2023-10-17 04:28:59 +0300
commit90de47f020db086f7929e09f64efd0cf627d6869 (patch)
tree92d37f1a0463536aad782523ba648474c8036970 /include/net/page_pool
parente411a8e3bb2d12a59d5fb3590863cb6a16f27b7a (diff)
downloadlinux-90de47f020db086f7929e09f64efd0cf627d6869.tar.xz
page_pool: fragment API support for 32-bit arch with 64-bit DMA
Currently page_pool_alloc_frag() is not supported in 32-bit arch with 64-bit DMA because of the overlap issue between pp_frag_count and dma_addr_upper in 'struct page' for those arches, which seems to be quite common, see [1], which means driver may need to handle it when using fragment API. It is assumed that the combination of the above arch with an address space >16TB does not exist, as all those arches have 64b equivalent, it seems logical to use the 64b version for a system with a large address space. It is also assumed that dma address is page aligned when we are dma mapping a page aligned buffer, see [2]. That means we're storing 12 bits of 0 at the lower end for a dma address, we can reuse those bits for the above arches to support 32b+12b, which is 16TB of memory. If we make a wrong assumption, a warning is emitted so that user can report to us. 1. https://lore.kernel.org/all/20211117075652.58299-1-linyunsheng@huawei.com/ 2. https://lore.kernel.org/all/20230818145145.4b357c89@kernel.org/ Tested-by: Alexander Lobakin <aleksander.lobakin@intel.com> Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com> CC: Lorenzo Bianconi <lorenzo@kernel.org> CC: Alexander Duyck <alexander.duyck@gmail.com> CC: Liang Chen <liangchen.linux@gmail.com> CC: Guillaume Tucker <guillaume.tucker@collabora.com> CC: Matthew Wilcox <willy@infradead.org> CC: Linux-MM <linux-mm@kvack.org> Link: https://lore.kernel.org/r/20231013064827.61135-2-linyunsheng@huawei.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'include/net/page_pool')
-rw-r--r--include/net/page_pool/helpers.h20
1 files changed, 14 insertions, 6 deletions
diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h
index 8e7751464ff5..8f64adf86f5b 100644
--- a/include/net/page_pool/helpers.h
+++ b/include/net/page_pool/helpers.h
@@ -197,7 +197,7 @@ 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 \
+#define PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA \
(sizeof(dma_addr_t) > sizeof(unsigned long))
/**
@@ -211,17 +211,25 @@ static inline dma_addr_t page_pool_get_dma_addr(struct page *page)
{
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;
+ if (PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA)
+ ret <<= PAGE_SHIFT;
return ret;
}
-static inline void page_pool_set_dma_addr(struct page *page, dma_addr_t addr)
+static inline bool page_pool_set_dma_addr(struct page *page, dma_addr_t addr)
{
+ if (PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA) {
+ page->dma_addr = addr >> PAGE_SHIFT;
+
+ /* We assume page alignment to shave off bottom bits,
+ * if this "compression" doesn't work we need to drop.
+ */
+ return addr != (dma_addr_t)page->dma_addr << PAGE_SHIFT;
+ }
+
page->dma_addr = addr;
- if (PAGE_POOL_DMA_USE_PP_FRAG_COUNT)
- page->dma_addr_upper = upper_32_bits(addr);
+ return false;
}
static inline bool page_pool_put(struct page_pool *pool)