From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ronny.Hegewald@online.de Subject: pvops dom0: no sound after boot; possibly caused by swiotlb Date: Tue, 26 Jan 2010 01:40:12 +0100 Message-ID: <20082315.3406621264466412554.JavaMail.servlet@kundenserver> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org Software: xen 3.4.1, lastest xen/master (version 2.6.31.6), both 32bit Hardware: Intel Core2Duo System 4GB Ram Realtek ALC888 soundchip Initial Symptoms: When playing audio in dom0 there are just "knock" sounds. After rmmod the kernel-module for the soundcard (snd-hda-intel) and oss modules (snd-seq-oss and snd-seq-pcm) and inserting them with modprobe again makes the sound work. Doing that only with snd-hda-intel doesnt help. I compiled the sound-modules directly into the kernel but that didnt changed anything. This problem doesnt appear with the gentoo-dom0 patches for kernel 2.6.31 so it looks like a pvops dom0 problem. Strangely that problem doesnt appear on another system with the same xen-version and the exactly same kernel. Main-difference is that the other system is a 2-core AMD-system with 2 GB Ram and a different soundcard. But starting the domU with only 2 GB didnt made any difference. Final findings: It finally turns out that when the sound-modules are loaded after a pv-domU is started the sound in domU works fine from the beginning. As i suspected a problem in the memory-layout that got "fixed" by the start of a PV-domU i started the domU with different memory-sizes and found out that the sound works fine if the domU is started with at least 66 MB. Everything under that and there is no sound (even the knock-sound is not there) The first thing i found that had could have to do with the 66 MB was the 64 MB swiotlb buffer. To check that this is really the problem i changed the code in arch/x86/xen/pci-swiotlb.c and lowered the allocated buffer to 32MB. After that change the sound worked from the beginning when the domU was started with less then 66 MB. Further investigations: >>From here i dont know at the moment how to investigate that problem further myself. Which logs should i post that could help to find the problem? What further steps could/should i do to investigate that myself?