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=-5.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 7BBCAC433DF for ; Mon, 18 May 2020 05:17:23 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 4CD7520787 for ; Mon, 18 May 2020 05:17:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="M0OEKKqq" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4CD7520787 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-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=bombadil.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=LrnLEmqF2FBDYw1OmtHFsFlaVud7HAg2kuj97L7vwPE=; b=M0OEKKqqqBdvNU3GECHTuruDO XhtRD/EFX6OOhryLZROmeSzImW4tv4zhGb1tOA2x+0AENEuaaS7jqD/wAs/e/rRGDCjWd0j5Ntr2q 6c94kKSBiEZXqvOw50IF/eu0HM2HWCV72ltUpge9rFVcoU/iEhq+LEOS67QvnobD03BGYggEipQAT vpYZVh/8ETOUcMasiReTnGMM9/Z9bd/3rGimvNn9tiM5m2Acb8+pnrALwVsaEGBhVI9JQWqaHddIv PbpRhgtPH7vpxKXorEO0oQ+TTE4fnrjvVKdJWl4hdVxQsK4HZKNV/p+Qn9IuZpAu2O9UpwEJ1sheZ tQu+Wq57Q==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jaY9S-0002D7-VD; Mon, 18 May 2020 05:17:22 +0000 Received: from mx2.suse.de ([195.135.220.15]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jaY9P-0002CM-Gp for linux-arm-kernel@lists.infradead.org; Mon, 18 May 2020 05:17:20 +0000 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id EF326ABE4; Mon, 18 May 2020 05:17:14 +0000 (UTC) Subject: Re: [PATCH v5 27/38] xen: gntdev: fix common struct sg_table related issues To: Marek Szyprowski , dri-devel@lists.freedesktop.org, iommu@lists.linux-foundation.org, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org References: <20200513132114.6046-1-m.szyprowski@samsung.com> <20200513133245.6408-1-m.szyprowski@samsung.com> <20200513133245.6408-27-m.szyprowski@samsung.com> From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= Message-ID: Date: Mon, 18 May 2020 07:17:09 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200513133245.6408-27-m.szyprowski@samsung.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200517_221719_702502_D72A22B1 X-CRM114-Status: GOOD ( 17.83 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Bartlomiej Zolnierkiewicz , David Airlie , Daniel Vetter , xen-devel@lists.xenproject.org, Boris Ostrovsky , Robin Murphy , Christoph Hellwig , linux-arm-kernel@lists.infradead.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 13.05.20 15:32, Marek Szyprowski wrote: > The Documentation/DMA-API-HOWTO.txt states that the dma_map_sg() function > returns the number of the created entries in the DMA address space. > However the subsequent calls to the dma_sync_sg_for_{device,cpu}() and > dma_unmap_sg must be called with the original number of the entries > passed to the dma_map_sg(). > > struct sg_table is a common structure used for describing a non-contiguous > memory buffer, used commonly in the DRM and graphics subsystems. It > consists of a scatterlist with memory pages and DMA addresses (sgl entry), > as well as the number of scatterlist entries: CPU pages (orig_nents entry) > and DMA mapped pages (nents entry). > > It turned out that it was a common mistake to misuse nents and orig_nents > entries, calling DMA-mapping functions with a wrong number of entries or > ignoring the number of mapped entries returned by the dma_map_sg() > function. > > To avoid such issues, lets use a common dma-mapping wrappers operating > directly on the struct sg_table objects and use scatterlist page > iterators where possible. This, almost always, hides references to the > nents and orig_nents entries, making the code robust, easier to follow > and copy/paste safe. > > Signed-off-by: Marek Szyprowski Acked-by: Juergen Gross Juergen _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel