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 00427C32750 for ; Tue, 13 Aug 2019 13:26:26 +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 C10C220844 for ; Tue, 13 Aug 2019 13:26:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C10C220844 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 5D3A7CA6; Tue, 13 Aug 2019 13:26:25 +0000 (UTC) Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 25CE3C86; Tue, 13 Aug 2019 13:26:23 +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 8777B12F; Tue, 13 Aug 2019 13:26:22 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id 77F5C68B02; Tue, 13 Aug 2019 15:26:17 +0200 (CEST) Date: Tue, 13 Aug 2019 15:26:17 +0200 From: Christoph Hellwig To: David Gibson Subject: Re: [RFC PATCH] virtio_ring: Use DMA API if guest memory is encrypted Message-ID: <20190813132617.GA6426@lst.de> References: <87zhrj8kcp.fsf@morokweng.localdomain> <20190810143038-mutt-send-email-mst@kernel.org> <20190810220702.GA5964@ram.ibm.com> <20190811055607.GA12488@lst.de> <20190812095156.GD3947@umbus.fritz.box> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190812095156.GD3947@umbus.fritz.box> User-Agent: Mutt/1.5.17 (2007-11-01) Cc: "Michael S. Tsirkin" , Benjamin Herrenschmidt , Jason Wang , Alexey Kardashevskiy , Ram Pai , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Paul Mackerras , iommu@lists.linux-foundation.org, linuxppc-devel@lists.ozlabs.org, Christoph Hellwig 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 Mon, Aug 12, 2019 at 07:51:56PM +1000, David Gibson wrote: > AFAICT we already kind of abuse this for the VIRTIO_F_IOMMU_PLATFORM, > because to handle for cases where it *is* a device limitation, we > assume that if the hypervisor presents VIRTIO_F_IOMMU_PLATFORM then > the guest *must* select it. > > What we actually need here is for the hypervisor to present > VIRTIO_F_IOMMU_PLATFORM as available, but not required. Then we need > a way for the platform core code to communicate to the virtio driver > that *it* requires the IOMMU to be used, so that the driver can select > or not the feature bit on that basis. I agree with the above, but that just brings us back to the original issue - the whole bypass of the DMA OPS should be an option that the device can offer, not the other way around. And we really need to fix that root cause instead of doctoring around it. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu