From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [Qemu-devel] [PATCH v5 06/16] apic: Introduce backend/frontend infrastructure for KVM reuse Date: Tue, 20 Dec 2011 07:41:12 -0600 Message-ID: <4EF09078.2030508@codemonkey.ws> References: <4EEFB72E.7030508@codemonkey.ws> <4EEFC970.9030205@web.de> <4EEFD69F.6080700@codemonkey.ws> <4EEFD786.8030609@web.de> <4EEFD90A.1000204@codemonkey.ws> <4EF05BC4.8010905@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Anthony Liguori , kvm@vger.kernel.org, "Michael S. Tsirkin" , Marcelo Tosatti , qemu-devel , Blue Swirl , Jan Kiszka To: Avi Kivity Return-path: Received: from mail-yx0-f174.google.com ([209.85.213.174]:49991 "EHLO mail-yx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752002Ab1LTNlP (ORCPT ); Tue, 20 Dec 2011 08:41:15 -0500 Received: by yenm11 with SMTP id m11so3990749yen.19 for ; Tue, 20 Dec 2011 05:41:14 -0800 (PST) In-Reply-To: <4EF05BC4.8010905@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 12/20/2011 03:56 AM, Avi Kivity wrote: > On 12/20/2011 02:38 AM, Anthony Liguori wrote: >>> That was v1 of my patches. Avi didn't like it, I tried it like this, and >>> in the end I had to agree. So, no, I don't think we want such a model. >> >> >> Yes, we do :-) >> >> The in-kernel APIC is a different implementation of the APIC device. >> It's not an "accelerator" for the userspace APIC. > > A different implementation but not a different device. Device == spec. If it was hardware, it'd be a fully compatible clone. The way we would model this is via inheritance. Regards, Anthony Liguori > >> >> All that you're doing here is reinventing qdev. You're defining your >> own type system (APICBackend), creating a new regression system for >> it, and then defining your own factory function for creating it >> (through a qdev property). >> >> I'm struggling to understand the reason to avoid using the >> infrastructure we already have to do all of this. > > Not every table of function pointers has to be done through qdev (not > that I feel strongly about this - only that there is just one APIC device). >