From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sasha Levin Subject: Guest kernel device compatability auto-detection Date: Thu, 25 Aug 2011 08:21:28 +0300 Message-ID: <1314249688.3459.23.camel@lappy> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Anthony Liguori , kvm To: qemu-devel Return-path: Received: from mail-ww0-f44.google.com ([74.125.82.44]:40754 "EHLO mail-ww0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750865Ab1HYFVb (ORCPT ); Thu, 25 Aug 2011 01:21:31 -0400 Received: by wwf5 with SMTP id 5so1959175wwf.1 for ; Wed, 24 Aug 2011 22:21:30 -0700 (PDT) Sender: kvm-owner@vger.kernel.org List-ID: Hi, Currently when we run the guest we treat it as a black box, we're not quite sure what it's going to start and whether it supports the same features we expect it to support when running it from the host. This forces us to start the guest with the safest defaults possible, for example: '-drive file=my_image.qcow2' will be started with slow IDE emulation even though the guest is capable of virtio. I'm currently working on a method to try and detect whether the guest kernel has specific configurations enabled and either warn the user if we know the kernel is not going to properly work or use better defaults if we know some advanced features are going to work. How am I planning to do it? First, we'll try finding which kernel the guest is going to boot (easy when user does '-kernel', less easy when the user boots an image). For simplicity sake I'll stick with the '-kernel' option for now. Once we have the kernel we can do two things: 1. See if the kernel was built with CONFIG_IKCONFIG. 2. Try finding the System.map which belongs to the kernel, it's provided with all distro kernels so we can expect it to be around. If we did find it we repeat the same process as in #1. If we found one of the above, we start matching config sets ("we need a,b,c,d for virtio, let's see if it's all there"). Once we find a good config set, we use it for defaults. If we didn't find a good config set we warn the user and don't even bother starting the guest. If we couldn't find either, we can just default to whatever we have as defaults now. To sum it up, I was wondering if this approach has been considered before and whether it sounds interesting enough to try. -- Sasha.