From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 55786EE4998 for ; Fri, 18 Aug 2023 21:52:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241087AbjHRVwO (ORCPT ); Fri, 18 Aug 2023 17:52:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32860 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240595AbjHRVvs (ORCPT ); Fri, 18 Aug 2023 17:51:48 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A61813C2D for ; Fri, 18 Aug 2023 14:51:47 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 3AC2560AF4 for ; Fri, 18 Aug 2023 21:51:47 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 17AB0C433C7; Fri, 18 Aug 2023 21:51:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1692395506; bh=+SAT99L6p9qOrwwqGuKFzj5xcLxv7JFhB1+eCLgFZuU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=dbh5QhQmBygkxwdLjiMPu2w5pXn7CeOAFhdOUPFyLloz6pyREQZO4qeRwk8861+dB 48k/D47ll89A2sUHd/iWhG9S9WorqufA78zTZNHnFVVphmJuclIFJVs0zvoHujLgmb c354+FtvkYl9dlDJnGillRdR3rmp8l770u2PHKMJ8NazQFBM6Cz+z2/7/HsLv+W39i OrB70Piv040gv7C2LMixbmAEAejRrsf9lO0J12pN/DfZNoouSYCnjvOCBZbsaGw3q6 6n32LWPpjJnEAos48GCHC2oVmrhuM0G1l/1HCH1jK5UY2dXtfv18z+jxq2/M8r3caG FAMxTr0urLxzw== Date: Fri, 18 Aug 2023 14:51:45 -0700 From: Jakub Kicinski To: Ilias Apalodimas Cc: Mina Almasry , Yunsheng Lin , davem@davemloft.net, pabeni@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Lorenzo Bianconi , Alexander Duyck , Liang Chen , Alexander Lobakin , Saeed Mahameed , Leon Romanovsky , Eric Dumazet , Jesper Dangaard Brouer Subject: Re: [PATCH net-next v7 1/6] page_pool: frag API support for 32-bit arch with 64-bit DMA Message-ID: <20230818145145.4b357c89@kernel.org> In-Reply-To: References: <20230816100113.41034-1-linyunsheng@huawei.com> <20230816100113.41034-2-linyunsheng@huawei.com> <20230817091554.31bb3600@kernel.org> <20230817165744.73d61fb6@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 18 Aug 2023 09:12:09 +0300 Ilias Apalodimas wrote: > > Right, IIUC we don't have enough space to fit dma_addr_t and the > > refcount, but if we store the dma addr on a shifted u32 instead > > of using dma_addr_t explicitly - the refcount should fit? > > struct page looks like this: > > unsigned long dma_addr; > union { > unsigned long dma_addr_upper; > atomic_long_t pp_frag_count; > }; I could be completely misunderstanding the problem. Let me show you the diff of what I was thinking more or less. diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 5e74ce4a28cd..58ffa8dc745f 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -126,11 +126,6 @@ struct page { 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. diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h index 94231533a369..6f87a0fa2178 100644 --- a/include/net/page_pool/helpers.h +++ b/include/net/page_pool/helpers.h @@ -212,16 +212,24 @@ 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; + 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) { + bool failed = false; + page->dma_addr = addr; - if (PAGE_POOL_DMA_USE_PP_FRAG_COUNT) - page->dma_addr_upper = upper_32_bits(addr); + if (PAGE_POOL_DMA_USE_PP_FRAG_COUNT) { + page->dma_addr >>= PAGE_SHIFT; + /* We assume page alignment to shave off bottom bits, + * if this "compression" doesn't work we need to drop. + */ + failed = addr != page->dma_addr << PAGE_SHIFT; + } + return failed; } 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..9ea42e242a89 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 +355,19 @@ 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: + 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,