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| author | Yunsheng Lin <linyunsheng@huawei.com> | 2023-10-13 14:48:21 +0800 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2023-10-16 18:28:59 -0700 |
| commit | 90de47f020db086f7929e09f64efd0cf627d6869 (patch) | |
| tree | 92d37f1a0463536aad782523ba648474c8036970 /include/linux/mm_types.h | |
| parent | e411a8e3bb2d12a59d5fb3590863cb6a16f27b7a (diff) | |
| download | linux-90de47f020db086f7929e09f64efd0cf627d6869.tar.gz linux-90de47f020db086f7929e09f64efd0cf627d6869.tar.bz2 linux-90de47f020db086f7929e09f64efd0cf627d6869.zip | |
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/linux/mm_types.h')
| -rw-r--r-- | include/linux/mm_types.h | 13 |
1 files changed, 1 insertions, 12 deletions
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 36c5b43999e6..74b49c4c7a52 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -125,18 +125,7 @@ struct page { struct page_pool *pp; unsigned long _pp_mapping_pad; unsigned long dma_addr; - 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; - }; + atomic_long_t pp_frag_count; }; struct { /* Tail pages of compound page */ unsigned long compound_head; /* Bit zero is set */ |