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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BEF26C433EF for ; Tue, 2 Nov 2021 06:42:05 +0000 (UTC) Received: from smtp4.osuosl.org (smtp4.osuosl.org [140.211.166.137]) (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 14C7A60720 for ; Tue, 2 Nov 2021 06:42:05 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 14C7A60720 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id D0335402CB; Tue, 2 Nov 2021 06:42:04 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id MPzAh28YtzLq; Tue, 2 Nov 2021 06:42:04 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [IPv6:2605:bc80:3010:104::8cd3:938]) by smtp4.osuosl.org (Postfix) with ESMTPS id AF1FC40125; Tue, 2 Nov 2021 06:42:03 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 68D8DC0019; Tue, 2 Nov 2021 06:42:03 +0000 (UTC) Received: from smtp1.osuosl.org (smtp1.osuosl.org [140.211.166.138]) by lists.linuxfoundation.org (Postfix) with ESMTP id 32870C000E for ; Tue, 2 Nov 2021 06:42:02 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id 2E96D80C4F for ; Tue, 2 Nov 2021 06:42:02 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id JunLqXYxyPj8 for ; Tue, 2 Nov 2021 06:42:01 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.8.0 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by smtp1.osuosl.org (Postfix) with ESMTPS id DAB3B80C49 for ; Tue, 2 Nov 2021 06:42:00 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id 7487768AA6; Tue, 2 Nov 2021 07:41:55 +0100 (CET) Date: Tue, 2 Nov 2021 07:41:55 +0100 From: Christoph Hellwig To: Walter Wu Subject: Re: [PATCH] dma-direct: fix DMA_ATTR_NO_KERNEL_MAPPING Message-ID: <20211102064155.GA27749@lst.de> References: <20211101031558.7184-1-walter-zh.wu@mediatek.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20211101031558.7184-1-walter-zh.wu@mediatek.com> User-Agent: Mutt/1.5.17 (2007-11-01) Cc: wsd_upstream , linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, linux-mediatek@lists.infradead.org, Matthias Brugger , Andrew Morton , Robin Murphy , Christoph Hellwig , linux-arm-kernel@lists.infradead.org X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" As others pointed out, DMA_ATTR_NO_KERNEL_MAPPING just means the caller can't rely on a kernel mapping. So the "fix" here is wrong. That being said for cases where we can easily remove a page from the kernel mapping it would be nice to do to: a) improve security b) as a debug check to see that no one actually tries to access it > + /* remove kernel mapping for pages */ > + set_memory_valid((unsigned long)phys_to_virt(dma_to_phys(dev, *dma_handle)), Please avoid overly long lines. Also this function only exists for arm64 also and others pointed out won't work for all cases. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu