From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1Mvu3Y-0001X6-Ir for qemu-devel@nongnu.org; Thu, 08 Oct 2009 10:33:24 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1Mvu3U-0001Uf-4V for qemu-devel@nongnu.org; Thu, 08 Oct 2009 10:33:24 -0400 Received: from [199.232.76.173] (port=35379 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Mvu3T-0001UR-OC for qemu-devel@nongnu.org; Thu, 08 Oct 2009 10:33:19 -0400 Received: from mail-qy0-f199.google.com ([209.85.221.199]:40228) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1Mvu3T-0000rd-CB for qemu-devel@nongnu.org; Thu, 08 Oct 2009 10:33:19 -0400 Received: by qyk37 with SMTP id 37so127395qyk.18 for ; Thu, 08 Oct 2009 07:33:18 -0700 (PDT) Message-ID: <4ACDF82B.4010200@codemonkey.ws> Date: Thu, 08 Oct 2009 09:33:15 -0500 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] Re: [PATCH v2 9/9] Add -kvm option 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> <1254953315-5761-6-git-send-email-glommer@redhat.com> <1254953315-5761-7-git-send-email-glommer@redhat.com> <1254953315-5761-8-git-send-email-glommer@redhat.com> <1254953315-5761-9-git-send-email-glommer@redhat.com> <1254953315-5761-10-git-send-email-glommer@redhat.com> <4ACD1D92.8080607@us.ibm.com> <4ACDF233.3090500@redhat.com> <4ACDF5D2.2070408@codemonkey.ws> <4ACDF779.2040505@redhat.com> In-Reply-To: <4ACDF779.2040505@redhat.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: Avi Kivity Cc: Mark McLoughlin , Anthony Liguori , Gerd Hoffmann , Glauber Costa , qemu-devel@nongnu.org Avi Kivity wrote: > On 10/08/2009 04:23 PM, Anthony Liguori wrote: >>>> What I'd like to see in the interim is a kvm specific machine type >>>> that's defaulted to if kvm is enabled. I think this would be >>>> useful not only for enabling things like in-kernel apic, but also >>>> for selecting a default cpu model. >>> >>> We should make a distinction between guest-visible changes and >>> accelerators like kvm-irqchip and vhost. >> >> They are different device models that happen to implement the same >> guest-visible device. > > I think this separation is artificial. From both the guest's view and > the user's view, there's no difference between qemu ioapic and kvm > ioapic (modulo bugs). To me this indicates they're the same device. That's not always been true historically. For instance, the in-kernel pit does interrupt catchup whereas the userspace pit does not. > We'll have the same problem with vhost-net, only there the duplication > will be much greater if we split the implementation. I'd rather not treat vhost-net like a device model and instead treat it like a -net backend. If we can bounce requests through userspace (and we can), we should be able to use it for any device model. In the case of virtio-net, we should be able to short-circuit things such that we don't have to go through userspace. It's admittedly very hairy without a point-to-point net abstraction. Regards, Anthony Liguori