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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 83F62C31E40 for ; Mon, 12 Aug 2019 12:13:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5C0A2208C2 for ; Mon, 12 Aug 2019 12:13:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728378AbfHLMN3 (ORCPT ); Mon, 12 Aug 2019 08:13:29 -0400 Received: from verein.lst.de ([213.95.11.211]:47869 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726200AbfHLMN3 (ORCPT ); Mon, 12 Aug 2019 08:13:29 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id 32BC4227A81; Mon, 12 Aug 2019 14:13:25 +0200 (CEST) Date: Mon, 12 Aug 2019 14:13:24 +0200 From: Christoph Hellwig To: Ram Pai Cc: Christoph Hellwig , "Michael S. Tsirkin" , Thiago Jung Bauermann , virtualization@lists.linux-foundation.org, linuxppc-devel@lists.ozlabs.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Jason Wang , David Gibson , Alexey Kardashevskiy , Paul Mackerras , Benjamin Herrenschmidt Subject: Re: [RFC PATCH] virtio_ring: Use DMA API if guest memory is encrypted Message-ID: <20190812121324.GA9405@lst.de> References: <87zhrj8kcp.fsf@morokweng.localdomain> <20190810143038-mutt-send-email-mst@kernel.org> <20190810220702.GA5964@ram.ibm.com> <20190811055607.GA12488@lst.de> <20190811064621.GB5964@ram.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190811064621.GB5964@ram.ibm.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Aug 10, 2019 at 11:46:21PM -0700, Ram Pai wrote: > If the hypervisor (hardware for hw virtio devices) does not mandate a > DMA API, why is it illegal for the driver to request, special handling > of its i/o buffers? Why are we associating this special handling to > always mean, some DMA address translation? Can't there be > any other kind of special handling needs, that has nothing to do with > DMA address translation? I don't think it is illegal per se. It is however completely broken if we do that decision on a system weide scale rather than properly requesting it through a per-device flag in the normal virtio framework. 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=-2.2 required=3.0 tests=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 9368DC433FF for ; Mon, 12 Aug 2019 12:13:30 +0000 (UTC) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org [140.211.169.12]) (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 720C9214C6 for ; Mon, 12 Aug 2019 12:13:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 720C9214C6 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from mail.linux-foundation.org (localhost [127.0.0.1]) by mail.linuxfoundation.org (Postfix) with ESMTP id 20BCFCB2; Mon, 12 Aug 2019 12:13:30 +0000 (UTC) Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 3CCCECAB; Mon, 12 Aug 2019 12:13:29 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id D4CB187D; Mon, 12 Aug 2019 12:13:28 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id 32BC4227A81; Mon, 12 Aug 2019 14:13:25 +0200 (CEST) Date: Mon, 12 Aug 2019 14:13:24 +0200 From: Christoph Hellwig To: Ram Pai Subject: Re: [RFC PATCH] virtio_ring: Use DMA API if guest memory is encrypted Message-ID: <20190812121324.GA9405@lst.de> References: <87zhrj8kcp.fsf@morokweng.localdomain> <20190810143038-mutt-send-email-mst@kernel.org> <20190810220702.GA5964@ram.ibm.com> <20190811055607.GA12488@lst.de> <20190811064621.GB5964@ram.ibm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190811064621.GB5964@ram.ibm.com> User-Agent: Mutt/1.5.17 (2007-11-01) Cc: "Michael S. Tsirkin" , Benjamin Herrenschmidt , Jason Wang , Alexey Kardashevskiy , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Paul Mackerras , iommu@lists.linux-foundation.org, linuxppc-devel@lists.ozlabs.org, Christoph Hellwig , David Gibson X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.12 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 Sender: iommu-bounces@lists.linux-foundation.org Errors-To: iommu-bounces@lists.linux-foundation.org On Sat, Aug 10, 2019 at 11:46:21PM -0700, Ram Pai wrote: > If the hypervisor (hardware for hw virtio devices) does not mandate a > DMA API, why is it illegal for the driver to request, special handling > of its i/o buffers? Why are we associating this special handling to > always mean, some DMA address translation? Can't there be > any other kind of special handling needs, that has nothing to do with > DMA address translation? I don't think it is illegal per se. It is however completely broken if we do that decision on a system weide scale rather than properly requesting it through a per-device flag in the normal virtio framework. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu