From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bernhard Schmidt Subject: Re: Freeze with KVM_CLOCK, undocumented dependency VIRTIO_BLK -> VIRTIO_PCI Date: Mon, 23 Jun 2008 01:22:32 +0200 Message-ID: <485EDEB8.3050109@birkenwald.de> References: <485DBBCD.5060600@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: Anthony Liguori Return-path: Received: from vs02.svr02.mucip.net ([83.170.6.69]:35226 "EHLO mailout.mucip.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755785AbYFVX3v (ORCPT ); Sun, 22 Jun 2008 19:29:51 -0400 In-Reply-To: <485DBBCD.5060600@codemonkey.ws> Sender: kvm-owner@vger.kernel.org List-ID: Hi, >> a) when I enable KVM_CLOCK in the kernel configuration the guest system >> freezes after >> >> PCI: Found IRQ 11 for device 0000:00:04.0 >> vda: vda1 vda2 >> TCP cubic registered >> NET: Registered protocol family 10 >> NET: Registered protocol family 17 >> Using IPI Shortcut mode > There are some outstanding patches for KVM_CLOCK that may fix this problem. Any pointers? I'd love to test and confirm. >> b) apparently VIRTIO_BLK works only when VIRTIO_PCI and thus PCI is >> enabled in the kernel. Otherwise the vda* device is not visible and the >> guest does not find its root filesystem. >> >> Is this expected? If yes, is it possible to add the appropriate >> dependency in the kernel configuration or amend the description >> accordingly? > VIRTIO_BLK doesn't depend on VIRTIO_PCI. VIRTIO_PCI allows you use to > virtio devices under KVM. I don't quite understand. VIRTIO_BLK can be selected in the kernel without selecting VIRTIO_PCI, it does not generate any build error but the virtual blockdevice simply does appear. Does VIRTIO_BLK have any use without VIRTIO_PCI? > This is all documented FWIW in the Kconfig and in a number of places on > the wiki. Where exactly in Kconfig? VIRTIO_BLK says nothing about VIRTIO_PCI or PCI, same for VIRTIO_NET. Yes, the VIRTIO_PCI Kconfig help says this "provides support for virtio based paravirtual device drivers over PCI". But this is far far away from the virtio drivers themselves, so one might not immediately notice that this is necessary. And if I disabled PCI completely (as a migrating Xen user who does not need PCI in domU at all) I won't even see the VIRTIO_PCI node, but still be able to select VIRTIO_BLK and _NET (which compile just fine but don't work, very confusing). Bernhard