From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: [Xen-devel] [PATCH RFC 0/3] Xen on Virtio Date: Mon, 14 Dec 2015 14:00:05 +0000 Message-ID: <566ECB65.3060509@citrix.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Stefano Stabellini , mst@redhat.com Cc: xen-devel@lists.xenproject.org, Andy Lutomirski , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org List-Id: virtualization@lists.linuxfoundation.org On 07/12/15 16:19, Stefano Stabellini wrote: > Hi all, > > this patch series introduces support for running Linux on top of Xen > inside a virtual machine with virtio devices (nested virt scenario). > The problem is that Linux virtio drivers use virt_to_phys to get the > guest pseudo-physical addresses to pass to the backend, which doesn't > work as expected on Xen. > > Switching the virtio drivers to the dma APIs (dma_alloc_coherent, > dma_map/unmap_single and dma_map/unmap_sg) would solve the problem, as > Xen support in Linux provides an implementation of the dma API which > takes care of the additional address conversions. However using the dma > API would increase the complexity of the non-Xen case too. We would also > need to keep track of the physical or virtual address in addition to the > dma address for each vring_desc to be able to free the memory in > detach_buf (see patch #3). > > Instead this series adds few obvious checks to perform address > translations in a couple of key places, without changing non-Xen code > paths. You are welcome to suggest improvements or alternative > implementations. Andy Lutomirski also looked at this. Andy what happened to this work? David From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753090AbbLNOAL (ORCPT ); Mon, 14 Dec 2015 09:00:11 -0500 Received: from smtp02.citrix.com ([66.165.176.63]:9164 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932592AbbLNOAI (ORCPT ); Mon, 14 Dec 2015 09:00:08 -0500 X-IronPort-AV: E=Sophos;i="5.20,427,1444694400"; d="scan'208";a="324877459" Message-ID: <566ECB65.3060509@citrix.com> Date: Mon, 14 Dec 2015 14:00:05 +0000 From: David Vrabel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.8.0 MIME-Version: 1.0 To: Stefano Stabellini , CC: , , , Andy Lutomirski Subject: Re: [Xen-devel] [PATCH RFC 0/3] Xen on Virtio References: In-Reply-To: Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-DLP: MIA2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/12/15 16:19, Stefano Stabellini wrote: > Hi all, > > this patch series introduces support for running Linux on top of Xen > inside a virtual machine with virtio devices (nested virt scenario). > The problem is that Linux virtio drivers use virt_to_phys to get the > guest pseudo-physical addresses to pass to the backend, which doesn't > work as expected on Xen. > > Switching the virtio drivers to the dma APIs (dma_alloc_coherent, > dma_map/unmap_single and dma_map/unmap_sg) would solve the problem, as > Xen support in Linux provides an implementation of the dma API which > takes care of the additional address conversions. However using the dma > API would increase the complexity of the non-Xen case too. We would also > need to keep track of the physical or virtual address in addition to the > dma address for each vring_desc to be able to free the memory in > detach_buf (see patch #3). > > Instead this series adds few obvious checks to perform address > translations in a couple of key places, without changing non-Xen code > paths. You are welcome to suggest improvements or alternative > implementations. Andy Lutomirski also looked at this. Andy what happened to this work? David