From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1MwLTq-0006S0-0D for qemu-devel@nongnu.org; Fri, 09 Oct 2009 15:50:22 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1MwLTk-0006Qk-Hl for qemu-devel@nongnu.org; Fri, 09 Oct 2009 15:50:20 -0400 Received: from [199.232.76.173] (port=56204 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1MwLTk-0006QT-By for qemu-devel@nongnu.org; Fri, 09 Oct 2009 15:50:16 -0400 Received: from e37.co.us.ibm.com ([32.97.110.158]:39464) by monty-python.gnu.org with esmtps (TLS-1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1MwLTj-0003c4-Si for qemu-devel@nongnu.org; Fri, 09 Oct 2009 15:50:16 -0400 Received: from d03relay02.boulder.ibm.com (d03relay02.boulder.ibm.com [9.17.195.227]) by e37.co.us.ibm.com (8.14.3/8.13.1) with ESMTP id n99JmwFP030260 for ; Fri, 9 Oct 2009 13:48:58 -0600 Received: from d03av03.boulder.ibm.com (d03av03.boulder.ibm.com [9.17.195.169]) by d03relay02.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id n99Jnp7U178906 for ; Fri, 9 Oct 2009 13:49:54 -0600 Received: from d03av03.boulder.ibm.com (loopback [127.0.0.1]) by d03av03.boulder.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id n99JngXp016270 for ; Fri, 9 Oct 2009 13:49:42 -0600 Message-ID: <4ACF93D5.3010002@us.ibm.com> Date: Fri, 09 Oct 2009 14:49:41 -0500 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] Re: [PATCH v2 4/9] provide in-kernel apic References: <1254953315-5761-1-git-send-email-glommer@redhat.com> <1254953315-5761-2-git-send-email-glommer@redhat.com> <1254953315-5761-3-git-send-email-glommer@redhat.com> <1254953315-5761-4-git-send-email-glommer@redhat.com> <1254953315-5761-5-git-send-email-glommer@redhat.com> <4ACDEF42.6020706@us.ibm.com> <4ACDF297.9010303@redhat.com> <20091008142202.GR8092@mothafucka.localdomain> <20091009100641.GC6576@shareable.org> <20091009143031.GU8092@mothafucka.localdomain> <20091009164831.GB7393@shareable.org> In-Reply-To: <20091009164831.GB7393@shareable.org> 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: Jamie Lokier Cc: Glauber Costa , Avi Kivity , kvm-devel , qemu-devel@nongnu.org Jamie Lokier wrote: > Glauber Costa wrote: > >> On Fri, Oct 09, 2009 at 11:06:41AM +0100, Jamie Lokier wrote: >> >>> Glauber Costa wrote: >>> >>>>> It ensures the two models are compatible. Since they're the same device >>>>> from the point of view of the guest, there's no reason for them to have >>>>> different representations or to be incompatible. >>>>> >>>> live migration between something that has in-kernel irqchip and >>>> something that has not is likely to be a completely untested >>>> thing. And this is the only reason we might think of it as the same >>>> device. I don't see any value in supporting this combination >>>> >>> Not just live migration. ACPI sleep + savevm + loadvm + ACPI resume, >>> for example. >>> >> Yes, but in this case too, I'd expect the irqchipness of qemu not to change. >> > > If I've just been sent an image produced by someone running KVM, and > my machine is not KVM-capable, or I cannot upgrade the KVM kernel > module because it's in use by other VMs (had this problem a few > times), there's no choice but to change the irqchipness. > You cannot migrate from KVM to TCG so this use-case is irrelevant. -- Regards, Anthony Liguori