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=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 1B444C3A589 for ; Thu, 15 Aug 2019 18:27:58 +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 E2D1D2063F for ; Thu, 15 Aug 2019 18:27:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="PvhgFDdq" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E2D1D2063F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de 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-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject: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=Th9QDD8OfK58xi/MJFQQagqcsP4yRNMiHzAI5mMEk+c=; b=PvhgFDdqBn3gfy jXWwOogxptrRWEwgfkhJKQRN4cLxM7ObRlg4vzZqjZwjgCYTKLheQg6o0UEhWgFCLDdiptafczuLU yzqIcoferdjPW99g55dYJR1WgmgaSWDl67go33++n3poiIf+7K2lmtcmrHVdtYTdw5SiOwYsoBmXb 93LR7EPLZJkTEIwKao04e/zMlNhOKKfLH0xx4laGsAjNrcWsiaALjA2SHoDdG0/FbiduwWrovbWjs C/KbactrOT5EtNyKLAK36EXc8WoyUR01Ug+vka7QadztDpDc8VhrtsTjJi4+eSoKyulGHlPW+cxby ehSEzc3OkKuY+5zSbvog==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hyKTd-00009g-IK; Thu, 15 Aug 2019 18:27:57 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1hyKTZ-00008b-1s for linux-arm-kernel@lists.infradead.org; Thu, 15 Aug 2019 18:27:55 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id EBED568AFE; Thu, 15 Aug 2019 20:27:42 +0200 (CEST) Date: Thu, 15 Aug 2019 20:27:42 +0200 From: Christoph Hellwig To: "Koenig, Christian" Subject: Re: [PATCH 0/6] drm+dma: cache support for arm, etc Message-ID: <20190815182742.GA20859@lst.de> References: <20190814220011.26934-1-robdclark@gmail.com> <20190815065117.GA23761@lst.de> <20190815175346.GA19839@lst.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: 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-20190815_112753_245303_801191A2 X-CRM114-Status: GOOD ( 15.41 ) 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: Kate Stewart , Masayoshi Mizuma , "Maciej W. Rozycki" , Eric Biggers , Catalin Marinas , Imre Deak , dri-devel , Chris Wilson , Masahiro Yamada , Benjamin Gaignard , Mauro Carvalho Chehab , Will Deacon , Christoph Hellwig , Emil Velikov , Rob Clark , Michael Ellerman , Paul Burton , Mike Rapoport , Geert Uytterhoeven , "moderated list:ARM64 PORT \(AARCH64 ARCHITECTURE\)" , Daniel Vetter , "open list:MIPS" , Linus Walleij , Robin Murphy , "open list:DRM DRIVER FOR MSM ADRENO GPU" , "Sharma, Deepak" , Joerg Roedel , Arnd Bergmann , Anshuman Khandual , Hauke Mehrtens , Jesper Dangaard Brouer , "Wolfram Sang \(Renesas\)" , "open list:LINUX FOR POWERPC \(32-BIT AND 64-BIT\)" , Alexios Zavras , Russell King , Doug Anderson , Thomas Gleixner , Sean Paul , Allison Randal , Christophe Leroy , Ard Biesheuvel , Enrico Weigelt , open list , Rob Clark , Souptick Joarder , Greg Kroah-Hartman , Andrew Morton , "open list:DRM DRIVER FOR MSM ADRENO GPU" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Aug 15, 2019 at 06:21:00PM +0000, Koenig, Christian wrote: > > (2) Add support for DMA_ATTR_NO_KERNEL_MAPPING to this new API instead > > of dma_alloc_attrs. The initial difference with that flag is just > > that we allow highmem, but in the future we could also unmap this > > memory from the kernel linear mapping entirely on architectures > > where we can easily do that. > > Mhm, why would we want to do this? To avoid the CPU misspeculating into this memory. For example NVMe SSDs have a feature called host memory buffer that is a lot like your stolen main ram for the GPU case. We currently hand the SSD a DMA_ATTR_NO_KERNEL_MAPPING allocation if it requests such a buffer. If possible we'd really like to make sure no speculative execution bug (or intentional attacker with a kernel exploit for that matter) can easily access that memory. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel