From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:47861) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TTNKL-0000FQ-Um for qemu-devel@nongnu.org; Tue, 30 Oct 2012 21:42:49 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TTNKK-0000Yv-Ta for qemu-devel@nongnu.org; Tue, 30 Oct 2012 21:42:41 -0400 Received: from [222.73.24.84] (port=17159 helo=song.cn.fujitsu.com) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TTNKK-0000Wz-G6 for qemu-devel@nongnu.org; Tue, 30 Oct 2012 21:42:40 -0400 Message-ID: <50908354.5070608@cn.fujitsu.com> Date: Wed, 31 Oct 2012 09:48:04 +0800 From: Wen Congyang MIME-Version: 1.0 References: <0a2274eccf1b1dd420f16359f7e1de74fa2f9fbe.1351131144.git.hutao@cn.fujitsu.com> <20121031011256.GC12325@amt.cnet> In-Reply-To: <20121031011256.GC12325@amt.cnet> Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=ISO-8859-1 Subject: Re: [Qemu-devel] [PATCH v11] kvm: notify host when the guest is panicked List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Marcelo Tosatti Cc: Andrew Jones , Gleb Natapov , kvm list , Hu Tao , qemu-devel , "linux-kernel@vger.kernel.org" , Blue Swirl , Avi Kivity , Jan Kiszka , Luiz Capitulino , KAMEZAWA Hiroyuki , Sasha Levin At 10/31/2012 09:12 AM, Marcelo Tosatti Wrote: > On Thu, Oct 25, 2012 at 11:42:32AM +0800, Hu Tao wrote: >> We can know the guest is panicked when the guest runs on xen. >> But we do not have such feature on kvm. >> >> Another purpose of this feature is: management app(for example: >> libvirt) can do auto dump when the guest is panicked. If management >> app does not do auto dump, the guest's user can do dump by hand if >> he sees the guest is panicked. >> >> We have three solutions to implement this feature: >> 1. use vmcall >> 2. use I/O port >> 3. use virtio-serial. >> >> We have decided to avoid touching hypervisor. The reason why I choose >> choose the I/O port is: >> 1. it is easier to implememt >> 2. it does not depend any virtual device >> 3. it can work when starting the kernel > > It has been asked earlier why a simple virtio device is not usable > for this (with no response IIRC). 1. We can't use virtio device when the kernel is booting. 2. The virtio's driver can be built as a module, and if it is not loaded and the kernel is panicked, there is no way to notify the host. 3. I/O port is more reliable than virtio device. If virtio's driver has some bug, and it cause kernel panicked, we can't use it. The I/O port is more reliable because it only depends on notifier chain(If we use virtio device, it also depends on notifier chain). Thanks Wen Congyang > > Also, there is no high level documentation: purpose of the interface, > how a management application should use it, etc. > >