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 D5552C433F5 for ; Tue, 2 Nov 2021 07:26:25 +0000 (UTC) Received: from smtp1.osuosl.org (smtp1.osuosl.org [140.211.166.138]) (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 8BA6660F02 for ; Tue, 2 Nov 2021 07:26:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 8BA6660F02 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=mediatek.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id 6165380C6D; Tue, 2 Nov 2021 07:26:25 +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 HsehJ5pKb4hP; Tue, 2 Nov 2021 07:26:24 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp1.osuosl.org (Postfix) with ESMTPS id 6155D80C15; Tue, 2 Nov 2021 07:26:24 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 347A4C0012; Tue, 2 Nov 2021 07:26:24 +0000 (UTC) Received: from smtp1.osuosl.org (smtp1.osuosl.org [IPv6:2605:bc80:3010::138]) by lists.linuxfoundation.org (Postfix) with ESMTP id 0BCF5C000E for ; Tue, 2 Nov 2021 07:26:23 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id E0EEF80C5A for ; Tue, 2 Nov 2021 07:26:22 +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 sXWgX1LTYiAl for ; Tue, 2 Nov 2021 07:26:18 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from mailgw01.mediatek.com (unknown [60.244.123.138]) by smtp1.osuosl.org (Postfix) with ESMTPS id 09F9080C15 for ; Tue, 2 Nov 2021 07:26:17 +0000 (UTC) X-UUID: e7445f08e2964818a4e40bd383f7fff4-20211102 X-UUID: e7445f08e2964818a4e40bd383f7fff4-20211102 Received: from mtkmbs10n2.mediatek.inc [(172.21.101.183)] by mailgw01.mediatek.com (envelope-from ) (Generic MTA with TLSv1.2 ECDHE-RSA-AES256-GCM-SHA384 256/256) with ESMTP id 1610379575; Tue, 02 Nov 2021 15:26:13 +0800 Received: from mtkmbs10n1.mediatek.inc (172.21.101.34) by mtkmbs10n1.mediatek.inc (172.21.101.34) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.792.15; Tue, 2 Nov 2021 15:26:12 +0800 Received: from mtksdccf07 (172.21.84.99) by mtkmbs10n1.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.2.792.15 via Frontend Transport; Tue, 2 Nov 2021 15:26:12 +0800 Message-ID: Subject: Re: [PATCH] dma-direct: fix DMA_ATTR_NO_KERNEL_MAPPING From: Walter Wu To: Christoph Hellwig Date: Tue, 2 Nov 2021 15:26:12 +0800 In-Reply-To: <20211102064155.GA27749@lst.de> References: <20211101031558.7184-1-walter-zh.wu@mediatek.com> <20211102064155.GA27749@lst.de> X-Mailer: Evolution 3.28.5-0ubuntu0.18.04.2 MIME-Version: 1.0 X-MTK: N Cc: wsd_upstream , linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, linux-mediatek@lists.infradead.org, Matthias Brugger , Andrew Morton , Robin Murphy , 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" Hi Christoph, I am sorry, fix my typo. Walter On Tue, 2021-11-02 at 07:41 +0100, Christoph Hellwig wrote: > 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