From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48151) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dEDbg-0008Rj-8J for qemu-devel@nongnu.org; Fri, 26 May 2017 07:40:39 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dEDbf-00073p-6d for qemu-devel@nongnu.org; Fri, 26 May 2017 07:40:36 -0400 Date: Fri, 26 May 2017 13:40:23 +0200 From: Kevin Wolf Message-ID: <20170526114023.GI7211@noname.str.redhat.com> References: <539d9960-d554-032f-3e88-b2531743a0a1@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] [Qemu-block] Behavior of QMP "query-block" List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Bruno Alvisio Cc: John Snow , qemu-devel@nongnu.org, Qemu-block Am 25.05.2017 um 20:44 hat Bruno Alvisio geschrieben: > Hello John, > > Thanks. Yes, typo when I wrote the e-mail. > > It might be possible that XEN does that (I will ask in the XEN forum). However, > I have noticed that it is not the case for all of the VMs I have launched. In > some of them I can query the block devices even after a long time the VM has > been running. > > I was wondering if the device is removed in case the disk is corrupted or > something. When I mention it runs normally, I can log into ithe VM and perform > read/write operations such creating files. > > Also, is there an easy way to log all qemu events so that I can see what might > be going on with the 'ide' device? There is one completely crazy thing that Xen does with respect to disks. Instead of having support for their PV disks (i.e. virtio-blk, just different) in the BIOS, they add _both_ an IDE disk and a PV disk to the VM, so that the bootloader or non-PV-aware guest OSes can access the IDE disk, for which they most certainly do have drivers. As soon as a driver for the PV disk is loaded, however, that driver calls a hypervisor function that removes all the IDE disks from the VM and leaves only the PV ones there, so that the PV-aware guest doesn't see two same disks. I suspect that what you're seeing initially is the IDE disks, and when the PV driver is loaded, they disappear. Kevin