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 019FEECE58E for ; Tue, 15 Oct 2019 07:35:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CDC212067B for ; Tue, 15 Oct 2019 07:35:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727579AbfJOHfJ (ORCPT ); Tue, 15 Oct 2019 03:35:09 -0400 Received: from verein.lst.de ([213.95.11.211]:53300 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725890AbfJOHfJ (ORCPT ); Tue, 15 Oct 2019 03:35:09 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id 4C96D68CEE; Tue, 15 Oct 2019 09:35:02 +0200 (CEST) Date: Tue, 15 Oct 2019 09:35:01 +0200 From: Christoph Hellwig To: Ram Pai Cc: linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, linuxppc-dev@lists.ozlabs.org, virtualization@lists.linux-foundation.org, benh@kernel.crashing.org, david@gibson.dropbear.id.au, mpe@ellerman.id.au, paulus@ozlabs.org, mdroth@linux.vnet.ibm.com, aik@linux.ibm.com, paul.burton@mips.com, robin.murphy@arm.com, b.zolnierkie@samsung.com, m.szyprowski@samsung.com, hch@lst.de, jasowang@redhat.com, andmike@us.ibm.com, sukadev@linux.vnet.ibm.com Subject: Re: [PATCH 2/2] virtio_ring: Use DMA API if memory is encrypted Message-ID: <20191015073501.GA32345@lst.de> References: <1570843519-8696-1-git-send-email-linuxram@us.ibm.com> <1570843519-8696-2-git-send-email-linuxram@us.ibm.com> <1570843519-8696-3-git-send-email-linuxram@us.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1570843519-8696-3-git-send-email-linuxram@us.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 Fri, Oct 11, 2019 at 06:25:19PM -0700, Ram Pai wrote: > From: Thiago Jung Bauermann > > Normally, virtio enables DMA API with VIRTIO_F_IOMMU_PLATFORM, which must > be set by both device and guest driver. However, as a hack, when DMA API > returns physical addresses, guest driver can use the DMA API; even though > device does not set VIRTIO_F_IOMMU_PLATFORM and just uses physical > addresses. Sorry, but this is a complete bullshit hack. Driver must always use the DMA API if they do DMA, and if virtio devices use physical addresses that needs to be returned through the platform firmware interfaces for the dma setup. If you don't do that yet (which based on previous informations you don't), you need to fix it, and we can then quirk old implementations that already are out in the field. In other words: we finally need to fix that virtio mess and not pile hacks on top of hacks.