From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:43512) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Q9yFD-00058p-G1 for qemu-devel@nongnu.org; Wed, 13 Apr 2011 07:28:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Q9yF6-0002qx-TS for qemu-devel@nongnu.org; Wed, 13 Apr 2011 07:28:23 -0400 Received: from david.siemens.de ([192.35.17.14]:31326) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Q9yF6-0002qf-FK for qemu-devel@nongnu.org; Wed, 13 Apr 2011 07:28:16 -0400 Message-ID: <4DA588C7.9010100@siemens.com> Date: Wed, 13 Apr 2011 13:28:07 +0200 From: Jan Kiszka MIME-Version: 1.0 References: <1301423290-12443-1-git-send-email-anthony.perard@citrix.com> <1301423290-12443-6-git-send-email-anthony.perard@citrix.com> <4D9F1249.6080305@siemens.com> <4DA35CC8.6030909@web.de> <4DA47551.90103@siemens.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH V12 05/17] xen: Add xenfv machine List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefano Stabellini Cc: Anthony Perard , Xen Devel , Alexander Graf , QEMU-devel On 2011-04-13 12:56, Stefano Stabellini wrote: > On Tue, 12 Apr 2011, Jan Kiszka wrote: >> Well, either you have a use for the VCPU state (how do you do migration >> in Xen without it?), or you should probably teach QEMU in a careful & >> clean way to run its device model without VCPUs - and without any >> TCG-related memory consumption. For the latter, you would likely receive >> kudos from KVM people as well. >> >> BTW, if you happen to support that crazy vmport under Xen, not updating >> the VCPU state will break your neck. Also, lacking VCPUs prevent the >> usage of analysis and debugging features of QEMU (monitor, gdbstub). > > We don't use the vcpu state in qemu because qemu takes care of device > emulation only; under xen the vcpu state is saved and restored by the > hypervisor. Just out of curiosity: So you are extracting the device states out of QEMU on migration, do the same with the VCPU states from the hypervisor (which wouldn't be that different from KVM in fact), and then transfer that to the destination node? Is there a technical or historical reason for this split-up? I mean, you still need some managing instance that does the state transportation and VM control on both sides, i.e. someone for the job that QEMU is doing for TCG or KVM migrations. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux