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 DAC2BC433EF for ; Tue, 2 Nov 2021 07:08:23 +0000 (UTC) Received: from smtp3.osuosl.org (smtp3.osuosl.org [140.211.166.136]) (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 7D54860E08 for ; Tue, 2 Nov 2021 07:08:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 7D54860E08 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 smtp3.osuosl.org (Postfix) with ESMTP id 367EA60071; Tue, 2 Nov 2021 07:08:23 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp3.osuosl.org ([127.0.0.1]) by localhost (smtp3.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 42pxfqKBCG8m; Tue, 2 Nov 2021 07:08:22 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp3.osuosl.org (Postfix) with ESMTPS id 30CB4600B8; Tue, 2 Nov 2021 07:08:22 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 13244C0012; Tue, 2 Nov 2021 07:08:22 +0000 (UTC) Received: from smtp4.osuosl.org (smtp4.osuosl.org [140.211.166.137]) by lists.linuxfoundation.org (Postfix) with ESMTP id EC08AC000E for ; Tue, 2 Nov 2021 07:08:20 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id D8BC54021C for ; Tue, 2 Nov 2021 07:08:20 +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 n2zax7G3OQvg for ; Tue, 2 Nov 2021 07:08:16 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from mailgw02.mediatek.com (unknown [210.61.82.184]) by smtp4.osuosl.org (Postfix) with ESMTPS id 893D44010E for ; Tue, 2 Nov 2021 07:08:16 +0000 (UTC) X-UUID: 9bc5c97f025f42dca1c5f591645a22ad-20211102 X-UUID: 9bc5c97f025f42dca1c5f591645a22ad-20211102 Received: from mtkmbs10n2.mediatek.inc [(172.21.101.183)] by mailgw02.mediatek.com (envelope-from ) (Generic MTA with TLSv1.2 ECDHE-RSA-AES256-GCM-SHA384 256/256) with ESMTP id 497361011; Tue, 02 Nov 2021 15:08:12 +0800 Received: from mtkcas11.mediatek.inc (172.21.101.40) by mtkmbs10n1.mediatek.inc (172.21.101.34) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id 15.2.792.15; Tue, 2 Nov 2021 15:08:11 +0800 Received: from mtksdccf07 (172.21.84.99) by mtkcas11.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Tue, 2 Nov 2021 15:08:11 +0800 Message-ID: <8903df2ad1ae1e0dfaafb3766beef7d0ec156f28.camel@mediatek.com> Subject: Re: [PATCH] dma-direct: fix DMA_ATTR_NO_KERNEL_MAPPING From: Walter Wu To: Christoph Hellwig Date: Tue, 2 Nov 2021 15:08:11 +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 Cristoph, 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 > I will modify my commit message. Thanks for your comment. > > + /* 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. Got it. I will send v2 patch. Thanks for your review and suggestion. Walter _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu