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 X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0869EC433ED for ; Sat, 17 Apr 2021 18:34:27 +0000 (UTC) Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7FBAA60FE5 for ; Sat, 17 Apr 2021 18:34:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7FBAA60FE5 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linaro.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=desiato.20200630; h=Sender:Content-Transfer-Encoding :Content-Type:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=ZpVSEfPcbgYBGFgmq9eo9/np6pdtclDaGWuJ2Ul+h0U=; b=KubVvLzoQNWEFB9H4zS4tK7tN hZ4u850YNPjNadUXa5xbow8U2Y8sJgR/OO5brGNh2qsJv7Rh8fyhhvS9EtYuB+QaV/OcGEZGVONTz 3LtJ7lGyrrYO2MdGwWx970zpobiSZcPh0yWWmZsMSFRE/DUz7Tli+1dEP6dChc9h8eT4O5e2RKoLX HsBIAakm+Rt+6LdRCnQ6eL9FrL4vrL/Ea2NjV2D5DB6vS7HWfJMpJklHTeiZLIwr0IWGEQ1APAtjf 7P/8i0b5b34nnD9wNhg3oRKdKt4VhcRWPxDno0dt8t+Hm93kd+KsPpQN+gK/ZLMf3+eLdSdAiCRIQ M9qyqJv1w==; Received: from localhost ([::1] helo=desiato.infradead.org) by desiato.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1lXpjw-005xn9-9t; Sat, 17 Apr 2021 18:32:20 +0000 Received: from bombadil.infradead.org ([2607:7c80:54:e::133]) by desiato.infradead.org with esmtps (Exim 4.94 #2 (Red Hat Linux)) id 1lXpjt-005xn0-24 for linux-arm-kernel@desiato.infradead.org; Sat, 17 Apr 2021 18:32:17 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=rXzu2aaQG3S7cGTxRDcxeH5itwSf5UHiBbc+Mfp3iik=; b=TrKJWyDdQkHZ4zsyZNy/NMtBEN eJaMLNkL3TexXMjEzwhU2eGmoMbBrDysm2q7nBxsepefvob4ijy7RB8gr0CDhtP00turlakLvJgTQ A+Fdxd7x0uEkCKo2kYnE9RSlvtCMu1CZ9JfPijSlSPEPLd9EFJQzOEKivrOHdLI79uJ6UJ7aK9RGr F50Qx8arIMcTkJjzXOiLlg3SHMbIHey3ACZuftEgKV3CNCj5m/TmUqQu4Br3lAglEFeVzyEtiQivY QgL8WhOW3PHRhFHCeAz+N/OrhE8sFSCyf3SMfp6XQwXmfgo9zZcfy71czfUSAAdYfyDT20+G25jxY HcCBTE3w==; Received: from mail-wm1-x333.google.com ([2a00:1450:4864:20::333]) by bombadil.infradead.org with esmtps (Exim 4.94 #2 (Red Hat Linux)) id 1lXpjn-00A93E-JI for linux-arm-kernel@lists.infradead.org; Sat, 17 Apr 2021 18:32:15 +0000 Received: by mail-wm1-x333.google.com with SMTP id w186so11435022wmg.3 for ; Sat, 17 Apr 2021 11:32:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=rXzu2aaQG3S7cGTxRDcxeH5itwSf5UHiBbc+Mfp3iik=; b=e9wLqXquNQTYWhXjUdKEFxVNM3EcZvI8CB4v0ovhwe/yevYVGVmzrbaHhE02CX0UKZ iAQ9XXHX1nTA8YswubW58TmD3iYRX4RADm9tE2JivkSsjiH4tHL6PevgUD+Q8o0lj13M Wh4WQNLWESeMTaegmO+swRQWtdK95e3TtBPFPjyoSMZO3m6jYk3AFl+7UJTVlzhYvukt kZIWWQL5KZN7mSFoC/bQUNXGH+80MdOC3b07Am6Bil612+h6z0k+ywWcIjHl/qR1rea2 iA5ItEuiIMldPKGr3Y9PSZWyZuR7p/rmUen+WySDnuz9aNuJAQg+hrIjwxVrU28R2S8P JYAw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=rXzu2aaQG3S7cGTxRDcxeH5itwSf5UHiBbc+Mfp3iik=; b=HQrsZ5RagIwjsuI1sKDKddu0Cn+2LHLLPp7pVbzVItrYbTpIkSTcrLeOjUxPS1wdic II1ERhatV+c3MxBRNKT2ZTFGMXmQbfnkOxBomy8+AclvCorTw1kDlAO0l87ogXihAO/p qMkKtofaWwvoW2lOqT1eART1t84QEqzNmaOBba8NkGn0nfB/HUNZgz7s+Ehffb1iAJOr V60IRzpvMh/mXZjlcP6b1aUfrOZ4PlPEiAeN+oM3Z9Y3FjxPZ2GX4vp+glGxjZpSN3sO g/GJTi1Kkiw19at/6pxkBG/RiWvpUlDyRaVfvMbMXGE+5CI7mfCSHZX7/7M7simuuGlb 139A== X-Gm-Message-State: AOAM530qadB78acHRD995kMJ96nRet05JjZPxoB/YH4GJBznGymfB+aW qUpnPJwu6m/UC1jbwMSk8uZEeA== X-Google-Smtp-Source: ABdhPJy8eVPGkCEVOqcITHVxTpCMYxsxuxYGe77mR9W540Za15SuA9f3s8LvAfJ6EElZzxF5pnQVxQ== X-Received: by 2002:a1c:770a:: with SMTP id t10mr13782514wmi.49.1618684329574; Sat, 17 Apr 2021 11:32:09 -0700 (PDT) Received: from apalos.home (ppp-94-65-92-88.home.otenet.gr. [94.65.92.88]) by smtp.gmail.com with ESMTPSA id a22sm15043900wrc.59.2021.04.17.11.32.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 17 Apr 2021 11:32:09 -0700 (PDT) Date: Sat, 17 Apr 2021 21:32:06 +0300 From: Ilias Apalodimas To: Matthew Wilcox Cc: brouer@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, mcroce@linux.microsoft.com, grygorii.strashko@ti.com, arnd@kernel.org, hch@lst.de, linux-snps-arc@lists.infradead.org, mhocko@kernel.org, mgorman@suse.de Subject: Re: [PATCH 1/2] mm: Fix struct page layout on 32-bit systems Message-ID: References: <20210416230724.2519198-1-willy@infradead.org> <20210416230724.2519198-2-willy@infradead.org> <20210417024522.GP2531743@casper.infradead.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210417024522.GP2531743@casper.infradead.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210417_113211_692953_ECF40226 X-CRM114-Status: GOOD ( 33.24 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Matthew, On Sat, Apr 17, 2021 at 03:45:22AM +0100, Matthew Wilcox wrote: > > Replacement patch to fix compiler warning. > > From: "Matthew Wilcox (Oracle)" > Date: Fri, 16 Apr 2021 16:34:55 -0400 > Subject: [PATCH 1/2] mm: Fix struct page layout on 32-bit systems > To: brouer@redhat.com > Cc: linux-kernel@vger.kernel.org, > linux-mm@kvack.org, > netdev@vger.kernel.org, > linuxppc-dev@lists.ozlabs.org, > linux-arm-kernel@lists.infradead.org, > linux-mips@vger.kernel.org, > ilias.apalodimas@linaro.org, > mcroce@linux.microsoft.com, > grygorii.strashko@ti.com, > arnd@kernel.org, > hch@lst.de, > linux-snps-arc@lists.infradead.org, > mhocko@kernel.org, > mgorman@suse.de > > 32-bit architectures which expect 8-byte alignment for 8-byte integers > and need 64-bit DMA addresses (arc, arm, mips, ppc) had their struct > page inadvertently expanded in 2019. When the dma_addr_t was added, > it forced the alignment of the union to 8 bytes, which inserted a 4 byte > gap between 'flags' and the union. > > Fix this by storing the dma_addr_t in one or two adjacent unsigned longs. > This restores the alignment to that of an unsigned long, and also fixes a > potential problem where (on a big endian platform), the bit used to denote > PageTail could inadvertently get set, and a racing get_user_pages_fast() > could dereference a bogus compound_head(). > > Fixes: c25fff7171be ("mm: add dma_addr_t to struct page") > Signed-off-by: Matthew Wilcox (Oracle) > --- > include/linux/mm_types.h | 4 ++-- > include/net/page_pool.h | 12 +++++++++++- > net/core/page_pool.c | 12 +++++++----- > 3 files changed, 20 insertions(+), 8 deletions(-) > > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h > index 6613b26a8894..5aacc1c10a45 100644 > --- a/include/linux/mm_types.h > +++ b/include/linux/mm_types.h > @@ -97,10 +97,10 @@ struct page { > }; > struct { /* page_pool used by netstack */ > /** > - * @dma_addr: might require a 64-bit value even on > + * @dma_addr: might require a 64-bit value on > * 32-bit architectures. > */ > - dma_addr_t dma_addr; > + unsigned long dma_addr[2]; > }; > struct { /* slab, slob and slub */ > union { > diff --git a/include/net/page_pool.h b/include/net/page_pool.h > index b5b195305346..ad6154dc206c 100644 > --- a/include/net/page_pool.h > +++ b/include/net/page_pool.h > @@ -198,7 +198,17 @@ static inline void page_pool_recycle_direct(struct page_pool *pool, > > static inline dma_addr_t page_pool_get_dma_addr(struct page *page) > { > - return page->dma_addr; > + dma_addr_t ret = page->dma_addr[0]; > + if (sizeof(dma_addr_t) > sizeof(unsigned long)) > + ret |= (dma_addr_t)page->dma_addr[1] << 16 << 16; > + return ret; > +} > + > +static inline void page_pool_set_dma_addr(struct page *page, dma_addr_t addr) > +{ > + page->dma_addr[0] = addr; > + if (sizeof(dma_addr_t) > sizeof(unsigned long)) > + page->dma_addr[1] = addr >> 16 >> 16; The 'error' that was reported will never trigger right? I assume this was compiled with dma_addr_t as 32bits (so it triggered the compilation error), but the if check will never allow this codepath to run. If so can we add a comment explaining this, since none of us will remember why in 6 months from now? > } > > static inline bool is_page_pool_compiled_in(void) > diff --git a/net/core/page_pool.c b/net/core/page_pool.c > index ad8b0707af04..f014fd8c19a6 100644 > --- a/net/core/page_pool.c > +++ b/net/core/page_pool.c > @@ -174,8 +174,10 @@ static void page_pool_dma_sync_for_device(struct page_pool *pool, > struct page *page, > unsigned int dma_sync_size) > { > + dma_addr_t dma_addr = page_pool_get_dma_addr(page); > + > dma_sync_size = min(dma_sync_size, pool->p.max_len); > - dma_sync_single_range_for_device(pool->p.dev, page->dma_addr, > + dma_sync_single_range_for_device(pool->p.dev, dma_addr, > pool->p.offset, dma_sync_size, > pool->p.dma_dir); > } > @@ -226,7 +228,7 @@ static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool, > put_page(page); > return NULL; > } > - page->dma_addr = dma; > + page_pool_set_dma_addr(page, dma); > > if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV) > page_pool_dma_sync_for_device(pool, page, pool->p.max_len); > @@ -294,13 +296,13 @@ void page_pool_release_page(struct page_pool *pool, struct page *page) > */ > goto skip_dma_unmap; > > - dma = page->dma_addr; > + dma = page_pool_get_dma_addr(page); > > - /* When page is unmapped, it cannot be returned our pool */ > + /* When page is unmapped, it cannot be returned to our pool */ > dma_unmap_page_attrs(pool->p.dev, dma, > PAGE_SIZE << pool->p.order, pool->p.dma_dir, > DMA_ATTR_SKIP_CPU_SYNC); > - page->dma_addr = 0; > + page_pool_set_dma_addr(page, 0); > skip_dma_unmap: > /* This may be the last page returned, releasing the pool, so > * it is not safe to reference pool afterwards. > -- > 2.30.2 > Thanks /Ilias _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel