Hi On Wed, 20 Sept 2023 at 11:59, Yunsheng Lin <linyunsheng@xxxxxxxxxx> wrote: > > On 2023/9/15 16:28, Jesper Dangaard Brouer wrote: > > Hi Lin, > > > > This looks reasonable, but given you are changing struct-page > > (include/linux/mm_types.h) we need to MM-list <linux-mm@xxxxxxxxx>. > > Also Cc Wilcox. > > > > I think it was Ilias and Duyck that validated the assumptions, last time > > this patch was discussed. Thus I want to see their review before this is > > applied. > > FWIW, PAGE_SIZE aligned buffer being PAGE_SIZE aligned in DMA is > validated by Duyck: > https://lore.kernel.org/all/CAKgT0UfeUAUQpEffxnkc+gzXsjOrHkuMgxU_Aw0VXSJYKzaovQ@xxxxxxxxxxxxxx/ > > And I had done researching to find out there seems to be no combination of > the above arch with an address space >16TB: > https://lore.kernel.org/all/2b570282-24f8-f23b-1ff7-ad836794baa9@xxxxxxxxxx/ Apologies for the late reply. I just saw you sent a v9, I'll review that instead, but I am traveling right now, will take a while Thanks /Ilias > > > > > -Jesper > > > > On 12/09/2023 10.31, Yunsheng Lin wrote: > >> 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 frag 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 aliged > >> 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@xxxxxxxxxx/ > >> 2. https://lore.kernel.org/all/20230818145145.4b357c89@xxxxxxxxxx/ > >> > >> Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx> > >> Signed-off-by: Yunsheng Lin <linyunsheng@xxxxxxxxxx> > >> CC: Lorenzo Bianconi <lorenzo@xxxxxxxxxx> > >> CC: Alexander Duyck <alexander.duyck@xxxxxxxxx> > >> CC: Liang Chen <liangchen.linux@xxxxxxxxx> > >> CC: Alexander Lobakin <aleksander.lobakin@xxxxxxxxx> > >> CC: Guillaume Tucker <guillaume.tucker@xxxxxxxxxxxxx> > >> --- > >> include/linux/mm_types.h | 13 +------------ > >> include/net/page_pool/helpers.h | 20 ++++++++++++++------ > >> net/core/page_pool.c | 14 +++++++++----- > >> 3 files changed, 24 insertions(+), 23 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 */ > >> diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h > >> index 94231533a369..8e1c85de4995 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) > >> diff --git a/net/core/page_pool.c b/net/core/page_pool.c > >> index 77cb75e63aca..8a9868ea5067 100644 > >> --- a/net/core/page_pool.c > >> +++ b/net/core/page_pool.c > >> @@ -211,10 +211,6 @@ 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; > >> - > >> #ifdef CONFIG_PAGE_POOL_STATS > >> pool->recycle_stats = alloc_percpu(struct page_pool_recycle_stats); > >> if (!pool->recycle_stats) > >> @@ -359,12 +355,20 @@ static bool page_pool_dma_map(struct page_pool *pool, struct page *page) > >> if (dma_mapping_error(pool->p.dev, dma)) > >> return false; > >> - page_pool_set_dma_addr(page, dma); > >> + if (page_pool_set_dma_addr(page, dma)) > >> + goto unmap_failed; > >> if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV) > >> page_pool_dma_sync_for_device(pool, page, pool->p.max_len); > >> return true; > >> + > >> +unmap_failed: > >> + WARN_ON_ONCE("unexpected DMA address, please report to netdev@"); > >> + dma_unmap_page_attrs(pool->p.dev, dma, > >> + PAGE_SIZE << pool->p.order, pool->p.dma_dir, > >> + DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_WEAK_ORDERING); > >> + return false; > >> } > >> static void page_pool_set_pp_info(struct page_pool *pool, > > > > . > >
