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 30E0EC433EF for ; Tue, 2 Nov 2021 06:43:10 +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 E918760E8C for ; Tue, 2 Nov 2021 06:43:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org E918760E8C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; 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=EIwEJwIeHnYidL8Jt0ptsjgLPV5UgWDqHDgGlrJjCmY=; b=cTshB94irYqDpV VhsB4BPrARi0Kqng0FfO4GYk6p6tlndW7/UplMJJUTbVvZN4145nbBeN07MkAzB1ZJ5dqeCWsPsfn vanGQ6hyejFw/s1xoekzKbWcJ20ZNixafs7AKGTuC76VeyG2a5rwBH2NOwk2V1hwOpdn/KgpxJnWc scT3gRWnEQz6pizUjnBcgcZRmoMWVMezCOIolOyLyC08ME7dhxgAtoPV6td350iFAPVMeCj3jeHje OrolNrJjTAlWfpNG5Ei/bmxcZIbq9EO/KtmCsNZll60McB+NUqr4tjS0/fA+k4QwGBCzLz5D/CvFU 4PP8fzmzA/Q1kIwcrBtg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mhnUg-000fUn-4I; Tue, 02 Nov 2021 06:42:02 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mhnUc-000fTt-Ii; Tue, 02 Nov 2021 06:41:59 +0000 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 Cc: Christoph Hellwig , Marek Szyprowski , Robin Murphy , Matthias Brugger , iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, wsd_upstream , linux-mediatek@lists.infradead.org, Andrew Morton 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) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211101_234158_788290_B841E33F X-CRM114-Status: GOOD ( 13.62 ) 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 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. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel