From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=57787 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Pcf7r-0004dF-3V for qemu-devel@nongnu.org; Tue, 11 Jan 2011 09:23:08 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Pcf7p-0005QV-OF for qemu-devel@nongnu.org; Tue, 11 Jan 2011 09:23:07 -0500 Received: from mx1.redhat.com ([209.132.183.28]:16226) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Pcf7p-0005QP-E7 for qemu-devel@nongnu.org; Tue, 11 Jan 2011 09:23:05 -0500 Message-ID: <4D2C67C2.5080000@redhat.com> Date: Tue, 11 Jan 2011 16:22:58 +0200 From: Avi Kivity MIME-Version: 1.0 Subject: Re: [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments References: <4D2616D6.4080309@linux.vnet.ibm.com> <4D26D6CF.5070405@web.de> <4D27A16F.9030809@linux.vnet.ibm.com> <4D282489.90506@web.de> <4D2B6506.6070907@linux.vnet.ibm.com> <4D2B6845.7050809@web.de> <4D2B6ADD.4090505@codemonkey.ws> <4D2C1C5D.2050504@redhat.com> <4D2C6290.1060607@linux.vnet.ibm.com> <1EA102F5-B6C2-43BC-9493-0271B287FC18@suse.de> <4D2C649F.6080508@linux.vnet.ibm.com> In-Reply-To: <4D2C649F.6080508@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: Marcelo Tosatti , Jan Kiszka , Alexander Graf , kvm@vger.kernel.org, qemu-devel@nongnu.org On 01/11/2011 04:09 PM, Anthony Liguori wrote: >> Disadvantages: >> >> 1) you lose migration / savevm between KVM and non-KVM VMs > > This doesn't work today and it's never worked. KVM exposes things > that TCG cannot emulate (like pvclock). If you run kvm without pvclock, or implement pvclock in qemu, it works fine. It should work fine for the PIT, PIC, and IOAPIC (never tried it myself). If we decide to have a kernel hpet implementation, for example, it would be good to be able to live migrate from a version without kernel hpet, to a version with kernel hpet, and have the kernel hpet enabled. > > Even as two devices, nothing prevents it from working. Both devices > just have to support each other's savevm format. If they use the same > code, it makes it very easy. Take a look at how the KVM PIT is > implemented for an example of this. They need to use the same device id then. And if they share code, that indicates that they need to be the same device even more. -- error compiling committee.c: too many arguments to function