From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1M9ffn-0005wt-H9 for qemu-devel@nongnu.org; Thu, 28 May 2009 09:29:31 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1M9ffi-0005rk-HX for qemu-devel@nongnu.org; Thu, 28 May 2009 09:29:30 -0400 Received: from [199.232.76.173] (port=33029 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1M9ffh-0005rG-NK for qemu-devel@nongnu.org; Thu, 28 May 2009 09:29:25 -0400 Received: from e8.ny.us.ibm.com ([32.97.182.138]:52792) by monty-python.gnu.org with esmtps (TLS-1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1M9ffh-0003gK-8b for qemu-devel@nongnu.org; Thu, 28 May 2009 09:29:25 -0400 Received: from d01relay04.pok.ibm.com (d01relay04.pok.ibm.com [9.56.227.236]) by e8.ny.us.ibm.com (8.13.1/8.13.1) with ESMTP id n4SDJ2Vp017742 for ; Thu, 28 May 2009 09:19:02 -0400 Received: from d01av04.pok.ibm.com (d01av04.pok.ibm.com [9.56.224.64]) by d01relay04.pok.ibm.com (8.13.8/8.13.8/NCO v9.2) with ESMTP id n4SDTO0o250266 for ; Thu, 28 May 2009 09:29:24 -0400 Received: from d01av04.pok.ibm.com (loopback [127.0.0.1]) by d01av04.pok.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id n4SDTNxD002354 for ; Thu, 28 May 2009 09:29:24 -0400 Message-ID: <4A1E91AF.9050907@us.ibm.com> Date: Thu, 28 May 2009 08:29:19 -0500 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH] Change virtio-console to PCI_CLASS_SERIAL_OTHER References: <1243012478.29542.18.camel@blaa> <200905281353.50463.paul@codesourcery.com> <4A1E8A16.3060101@us.ibm.com> <200905281422.52420.paul@codesourcery.com> In-Reply-To: <200905281422.52420.paul@codesourcery.com> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paul Brook Cc: Mark McLoughlin , Dor Laor , ajax@redhat.com, qemu-devel@nongnu.org Paul Brook wrote: >>>> - the device model cannot change or the guest OS will get confused >>>> >>> IMHO think the only sane response is "don't do that". Trying to support >>> migration between different qemu versions just isn't worth the pain. >>> >> It is very worth the pain. I consider it a core requirement. >> > > We disagree then. You're effectively requiring bug-compatibility. > You can take it to an extreme and require bug-compatibility, but I don't think that's necessary. I think there's room for being reasonable. > This may be reasonable for a stable branch, but is not something I have any > interest in across different release cycles. IMHO major VM upgrades should be > considered the same as real hardware or firmware upgrades. > I think major VM upgrades is something that can be considered occasionally but every 6 months would be pretty painful to most users. I think we ought to make a best effort to maintain compatibility with older versions as long as it's reasonable. Regards, Anthony Liguori > Paul >