xen July 2008

xen@lists.fedoraproject.org

24 participants
18 discussions

Guest shutdown problems
by Christian Axelsson 02 Apr '09

02 Apr '09

Hello I have a problem shutting down xen guests. Using xm shutdown guests get shut down but gets stuck in state '---s-d' or sometimes '------'. When trying to clone a domain when in this state (my original purpose of the whole operation) I'll get the error: [root@hydra virtinst--devel]# ./virt-clone -o minimal -n new_img -f /var/lib/xen/images/new_img.img ERROR: virDomainGetXMLDesc() failed failed Xen syscall xenDaemonDomainDumpXMLByID failed to find this domain -490299505 The same errors occurs when for example trying to attach to the console using virsh. I have tried to use 'xm destroy' to kill the guest the hard way but it has no effect - the state remains unchanged. I have also tried this on a few different guest installations with the same result. A thing worth noting is that the output from 'xm list --long' differs, I've attached the out put pre boot, after boot and after shutdown. Note how all the devices in the guests are missing after shutdown. Both the hosts and the guests are fedora 8 installations. Regards, Christian Axelsson smiler(a)lanil.mine.nu [?1034h(domain (domid 0) (on_crash restart) (uuid 00000000-0000-0000-0000-000000000000) (bootloader_args ) (vcpus 2) (name Domain-0) (on_poweroff destroy) (on_reboot restart) (bootloader ) (maxmem 16777215) (memory 1491) (shadow_memory 0) (cpu_weight 256) (cpu_cap 0) (features ) (on_xend_start ignore) (on_xend_stop ignore) (cpu_time 1644.84369405) (online_vcpus 2) (image (linux (kernel ))) (status 2) (state r-----) ) (domain (domid 2) (on_crash restart) (uuid a7638797-e237-3891-5e64-390f828238ca) (bootloader_args ) (vcpus 1) (name minimal) (on_poweroff destroy) (on_reboot restart) (bootloader /usr/bin/pygrub) (maxmem 512) (memory 512) (shadow_memory 0) (cpu_weight 256) (cpu_cap 0) (features ) (on_xend_start ignore) (on_xend_stop ignore) (start_time 1206360333.14) (cpu_time 9.753408915) (online_vcpus 1) (image (linux (kernel ) (notes (FEATURES 'writable_page_tables|writable_descriptor_tables|auto_translated_physmap|pae_pgdir_above_4gb|supervisor_mode_kernel' ) (VIRT_BASE 18446744071562067968) (GUEST_VERSION 2.6) (PADDR_OFFSET 18446744071562067968) (GUEST_OS linux) (HYPERCALL_PAGE 18446744071564189696) (LOADER generic) (SUSPEND_CANCEL 1) (ENTRY 18446744071564165120) (XEN_VERSION xen-3.0) ) ) ) (status 2) (state -b----) (store_mfn 196619) (console_mfn 196618) (device (vif (bridge xenbr0) (mac 00:16:3e:3f:93:b8) (script vif-bridge) (uuid 94afd732-920b-2e0b-b3d5-e79174754a80) (backend 0) ) ) (device (vbd (uname file:/var/lib/xen/images/minimal.img) (uuid 8f4f4da3-5f8a-3fee-28e8-41dc49e876cd) (mode w) (dev xvda:disk) (backend 0) (bootable 1) ) ) (device (console (protocol vt100) (location 2) (uuid 0046f2d3-058b-d524-9273-f1dac2ca950b) ) ) ) [?1034h(domain (domid 0) (on_crash restart) (uuid 00000000-0000-0000-0000-000000000000) (bootloader_args ) (vcpus 2) (name Domain-0) (on_poweroff destroy) (on_reboot restart) (bootloader ) (maxmem 16777215) (memory 1491) (shadow_memory 0) (cpu_weight 256) (cpu_cap 0) (features ) (on_xend_start ignore) (on_xend_stop ignore) (cpu_time 1648.92600832) (online_vcpus 2) (image (linux (kernel ))) (status 2) (state r-----) ) (domain (domid 2) (on_crash restart) (uuid a7638797-e237-3891-5e64-390f828238ca) (bootloader_args ) (vcpus 1) (name minimal) (on_poweroff destroy) (on_reboot restart) (bootloader /usr/bin/pygrub) (maxmem 512) (memory 512) (shadow_memory 0) (cpu_weight 256) (cpu_cap 0) (features ) (on_xend_start ignore) (on_xend_stop ignore) (start_time 1206360333.14) (cpu_time 13.048743365) (online_vcpus 1) (image (linux (kernel ) (notes (FEATURES 'writable_page_tables|writable_descriptor_tables|auto_translated_physmap|pae_pgdir_above_4gb|supervisor_mode_kernel' ) (VIRT_BASE 18446744071562067968) (GUEST_VERSION 2.6) (PADDR_OFFSET 18446744071562067968) (GUEST_OS linux) (HYPERCALL_PAGE 18446744071564189696) (LOADER generic) (SUSPEND_CANCEL 1) (ENTRY 18446744071564165120) (XEN_VERSION xen-3.0) ) ) ) (status 0) (state ---s-d) (store_mfn 196619) (console_mfn 196618) ) [?1034h(domain (domid 0) (on_crash restart) (uuid 00000000-0000-0000-0000-000000000000) (bootloader_args ) (vcpus 2) (name Domain-0) (on_poweroff destroy) (on_reboot restart) (bootloader ) (maxmem 16777215) (memory 1491) (shadow_memory 0) (cpu_weight 256) (cpu_cap 0) (features ) (on_xend_start ignore) (on_xend_stop ignore) (cpu_time 1635.21430615) (online_vcpus 2) (image (linux (kernel ))) (status 2) (state r-----) ) (domain (on_crash restart) (uuid a7638797-e237-3891-5e64-390f828238ca) (bootloader_args ) (vcpus 1) (name minimal) (on_poweroff destroy) (on_reboot restart) (bootloader /usr/bin/pygrub) (maxmem 512) (memory 512) (shadow_memory 0) (cpu_weight 256) (cpu_cap 0) (features ) (on_xend_start ignore) (on_xend_stop ignore) (start_time 1206309092.82) (cpu_time 0.0) (image (linux (kernel ) (notes (FEATURES 'writable_page_tables|writable_descriptor_tables|auto_translated_physmap|pae_pgdir_above_4gb|supervisor_mode_kernel' ) (VIRT_BASE 18446744071562067968) (GUEST_VERSION 2.6) (PADDR_OFFSET 18446744071562067968) (GUEST_OS linux) (HYPERCALL_PAGE 18446744071564189696) (LOADER generic) (SUSPEND_CANCEL 1) (ENTRY 18446744071564165120) (XEN_VERSION xen-3.0) ) ) ) (status 0) (device (vif (bridge xenbr0) (mac 00:16:3e:3f:93:b8) (backend 0) (uuid 94afd732-920b-2e0b-b3d5-e79174754a80) (script vif-bridge) ) ) (device (vbd (uuid 8f4f4da3-5f8a-3fee-28e8-41dc49e876cd) (bootable 1) (driver paravirtualised) (dev xvda:disk) (uname file:/var/lib/xen/images/minimal.img) (mode w) (backend 0) ) ) (device (console (protocol vt100) (location 2) (uuid 0046f2d3-058b-d524-9273-f1dac2ca950b) ) ) )

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problems with f9 guest on f8 dom0
by Matt Cowan 22 Sep '08

22 Sep '08

Anytime I shutdown or restart (the guest will successfully restart) an f9 guest on an f8 dom0 it causes virt-manager to hang and virt-install to fail. Attempts to restart virt-manager hang at "Connecting". no luck restarting xend, libvirtd, or even xenstored, only solution I've found is a dom0 reboot! Same problem on 2 different host systems, different hardware, dom0 installed by different people. I have no trouble with <=f8 guests on either of these boxes. more details at https://bugzilla.redhat.com/show_bug.cgi?id=429403#c7 I assume other people are successfully running f9 guests on f8 dom0?! No one else having this issue? thanks. -matt

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F10 crystal ball gazing
by Andy Burns 23 Aug '08

23 Aug '08

Given that xen is entering feature freeze for updated release ~August is it too early to ask what the *hopes* are for xen in fedora10? xen 3.3.0 (or late rc) or is this still likely to be 3.2.1 or 3.2.2? kernel 2.6.27(or late rc) with pv_ops for 32 and 64 bit, dom0 and domU? oVirt? updates to libvirt/virt-manager as usual

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[Xen-devel] State of Xen in upstream Linux
by Pasi Kärkkäinen 01 Aug '08

01 Aug '08

----- Forwarded message from Jeremy Fitzhardinge <jeremy(a)goop.org> ----- From: Jeremy Fitzhardinge <jeremy(a)goop.org> To: Xen-devel <xen-devel(a)lists.xensource.com>, xen-users(a)lists.xensource.com, Virtualization Mailing List <virtualization(a)lists.osdl.org> Cc: Date: Wed, 30 Jul 2008 17:51:37 -0700 Subject: [Xen-devel] State of Xen in upstream Linux Well, the mainline kernel just hit 2.6.27-rc1, so it's time for an update about what's new with Xen. I'm trying to aim this at both the user and developer audiences, so bear with me if I seem to be waffling about something irrelevant. 2.6.26 was mostly a bugfix update compared with 2.6.25, with a few small issues fixed up. Feature-wise, it supports 32-bit domU with the core devices needed to make it work (netfront, blockfront, console). It also has xen-pvfb support, which means you can run the standard X server without needing to set up Xvnc. I don't know of any bugs in 2.6.26, so I'd recommend you try it out for all your 32-bit domU needs. It has had fairly wide exposure in Fedora kernels, so I'd rank its stability as fairly high. If you're migrating from 2.6.18-xen, then there'll be a few things you need to pay attention to. http://wiki.xensource.com/xenwiki/XenParavirtOps should help, but if it doesn't, please either fix it and/or ask! 2.6.27 will be a much more interesting release. It has two major feature additions: save/restore/migrate (including checkpoint and live migration), and x86-64 support. In keeping with the overall unification of i386 and x86-64 code in the kernel, the 32- and 64-bit Xen code is largely shared, so they have feature parity. The Xen support seems fairly stable in linux-2.6.git, but the kernel is still at -rc1, so lots of other things will tend to break. I encourage you to try it out if you're comfortable with what's still a fairly high rate of change. My current patch stack is pretty much empty - everything has been merged into linux-2.6.git - so it makes a good base for any changes you may have Now that Xen can directly boot a bzImage format kernel, distros have a lot of flexibilty in how they package Xen. A single grub.conf entry can be used to boot either a native kernel (via normal grub), or a paravirtualized Xen kernel (via pygrub), without modification. Fedora 9's kernel-xen package has been based on the mainline kernel from the outset, but it is still packaged as a separate kernel. kernel-xen has been dropped from rawhide (what will become Fedora 10), and all Xen support - both 32 and 64 bit - has been rolled into the main kernel package. So, what's next? The obvious big piece of missing functionality is dom0 support. That will be my focus in this next kernel development window, and I hope we'll have it merged into 2.6.28. Some roadblock may appear which prevents this (kernel development is always a bit uncertain), but that's the current plan. We're planning on setting up a xen.git on xen.org somewhere. We still need to work out the precise details, but my expectation is that will become the place where dom0 work continues, and I also hope that other Xen developers will start using it as the base for their own Xen work. Expect to see some more concrete details over the next week or so. What can I do? I'm glad you asked. Here's my current TODO list. These are mostly fairly small-scale projects which just need some attention. I'd love people to adopt things from this list. x86-64: SMP broken with CONFIG_PREEMPT It crashes early after bringing up a second CPU when preempt is enabled. I think it's failing to set up the CPU topology properly, and leaving something uninitialized. The desired topology is the simplest possible - one core per package, no SMT/HT, no multicore, no shared caches. It should be simple to set up. irq balancing causes lockups Using irq balancing causes the kernel to lock up after a while. It looks like it's losing interrupts. It's probably dropping interrupts if you migrate an irq beween vcpus while an event is pending. Shouldn't be too hard to fix. (In the meantime, the workaround is to make sure that you don't enable in-kernel irq balancing, and you don't run irqbalanced.) block device hotplug Hotplugging devices should work already, but I haven't really tested it. Need to make sure that both the in-kernel driver stuff works properly, and that udev events are raised properly, scripts run, device nodes added - and conversely for unplug. Also, a modular xen-blockfront.ko should be unloadable. net device hotplug Similar to block devices, but with a slight extra complication. If the driver has outstanding granted pages, then the module can't be immediately unloaded, because you can't free the pages if dom0 has a reference to them. My thought is to add a simple kernel thread which takes ownership of unwanted granted pages: it would periodically try to ungrant them, and if successful, free the page. That means that netfront could hand ownership of those pages over to that thread, and unload immediately. Performance measurement and tuning By design, the paravirt-ops-based Xen implementation should have high performance. It uses batching where-ever possible, late pin/early unpin, and all the other performance tricks available to a Xen kernel. However, my emphasis has been on correctness and features, so I have not extensively benchmarked or performance tuned the code. There's plenty of scope for measuring both synthetic and real-world benchmarks (ideally, applications you really care about), and try to work out how things can be tuned. One thing that has already come to light is a general regression in context switch time compared to 2.6.18.8-xen. It's unclear where it's coming from; a close look at the actual context switch code itself shows that it should perform the same as 2.6.18-xen (same number of hypercalls performed, for example). This would be an excellent opportunity to become familiar with Xen's tracing and performance measurement tools... Balloon driver The current in-kernel balloon driver only supports shrinking and regrowing a domain up to its original size. There's no support for growing a domain beyond that. My plan is to use hotplug memory to add new memory to the system. I have some prototype code to do this, which works OK, but the hotplug memory subsystem needs some modifications to really deal with the kinds of incremental memory increases that we need for ballooning (it assumes that you're actually plugging in physical DIMMs). The other area which needs attention is some sanity checking when deflating a domain, to prevent killing the domain by stealing too much memory. 2.6.18-xen uses a simple static minimum memory heuristic based on the original size of the domain. This helps, but doesn't really prevent over-shrinking a domain which is already under memory pressure. A better approach might be to register a shrinker callback, which means that the balloon driver can see how much memory pressure the system is under by looking getting feedback from it. A more advanced project is to modify the kernel VM subsystem to measure refault distance, which is how long a page is evicted before being faulted back in again. That measurement can tell you how much more memory you need to add to a domain in order to get the fault rate below a given rate. gdb gives bad info in a 64-bit domain For some reason, gdb doesn't work properly. If you set a breakpoint, the program will stop as expected, but the register state will be wrong. Other users of the ptrace syscall, such as strace, seem to get good results, so I'm not sure what's going on here. It might be a simple fix, or symptomatic of a more serious problem. But it needs investigation first. My Pet Project What's missing? What do you depend on? What's needed before you can use mainline Xen as your sole Xen kernel? Thanks, J

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diskless boot
by Luca 29 Jul '08

29 Jul '08

Hi all, following the fedora-xen instruction, I was able to install XEN and Domain 0 and create an initial ram disk with mkinitrd (which will then mount the real root filesystem located on an hard drive on the same workstation). I wonder if what follows, is possible. On a workstation, I would not install anything. Instead I would use etherboot, for instance, to download Xen hypervisor, Domain 0 and an initial ram disk from a server. Everything would be loaded in memory. The initial ram disk would then mount the real root filesystem, located this time not on the same workstation, but on a different workstation connected to the network. I have tried building by myself an initial ram disk capable of mounting a real filesystem located on a different workstation but it didn't work. I'm not a fedora or Xen expert, so I hope someone here could help me. Of course, I assume the NFS server is working. Thanks, Luca

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source code
by Luca 28 Jul '08

28 Jul '08

Hi all, I'm using Fedora 8. With yum install xen yum groupinstall 'Virtualization' I can install XEN and Domain 0 and everything works. Now I would like to get the source code for the version of XEN and the kernel installed with the previous commands (I eventually need to modify and recompile them). How can I get the source code? Thanks in advance. Luca

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kernel-xen is dead
by Mark McLoughlin 27 Jul '08

27 Jul '08

Hey, When this build finishes: http://koji.fedoraproject.org/koji/buildinfo?buildID=57402 rawhide kernel-PAE.i686 and kernel.x86_64 will contain support for i686 and x86_64 Xen DomU guests. We've added Obsoletes/Provides, so a simple yum update should work fine[1]. Today the world has been made a little more sane. Rejoice :-) Cheers, Mark. [1] - With the caveat that the new kernel won't be made the default in grub.conf ... I'll fix up that soon, see: https://bugzilla.redhat.com/show_bug.cgi?id=456558

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Testing LiveCD distros as guests?
by Philip Rhoades 26 Jul '08

26 Jul '08

People, I want to test out a bunch of LiveCD distributions - is it possible to set these up as guests under Xen so I don't have to shut down my main machine? Thanks, Phil. -- Philip Rhoades Pricom Pty Limited (ACN 003 252 275 ABN 91 003 252 275) GPO Box 3411 Sydney NSW 2001 Australia E-mail: phil(a)pricom.com.au

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New kernel-xen in rawhide
by Mark McLoughlin 24 Jul '08

24 Jul '08

Hi, Just a heads up that I'm pushing a new 2.6.27 based kernel-xen to rawhide. This includes Jeremy Fitzhardinge's xen-64bit tree[1] in place of Eduardo's xen-pvops-64.git tree. Basically, Jeremy has half of the 64 bit Xen work merged for 2.6.27 already and the other half is queued up, hopefully to be included before the merge window ends. If we can get that stuff some testing, perhaps it might help the cause of getting it merged. This is all irrelevant if the build fails, of course :-) http://koji.fedoraproject.org/koji/taskinfo?taskID=725025 Cheers, Mark. [1] - http://git.kernel.org/?p=linux/kernel/git/x86/linux-2.6-x86.git;a=shortlog;…

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How to kill a domU that has no id
by Gerhard Scheffler 21 Jul '08

21 Jul '08

How to kill a domU that has no id? # xm list Name ID Mem VCPUs State Time(s) Domain-0 0 512 2 r----- 2745.2 m1 1 1024 2 -b---- 7764.6 m3 2 1024 2 -b---- 6765.8 m4 5 512 2 -b---- 1032.5 m5 512 2 0.0 Does m5 realy consume memory? xm lists m5 even after dom0 reboot. Gerhard

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xen July 2008