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| kb:linux:kvm:hyperv_enightments [2015/12/12 21:16] – milano | kb:linux:kvm:hyperv_enightments [2015/12/12 21:32] (current) – milano |
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| ==== Enabling Hyper-V enlightenments with KVM ==== | ====== Enabling Hyper-V enlightenments with KVM ====== |
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| | Author: [[http://blog.wikichoon.com/2014/07/enabling-hyper-v-enlightenments-with-kvm.html|Cole Robins]] |
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| | Windows has support for several paravirt features that it will use when running on Hyper-V, Microsoft's hypervisor. These features are called enlightenments. Many of the features are similar to paravirt functionality that exists with Linux on KVM (virtio, kvmclock, PV EOI, etc.) |
| | |
| | Nowadays QEMU/KVM can also enable support for several Hyper-V enlightenments. When enabled, Windows VMs running on KVM will use many of the same paravirt optimizations they would use when running on Hyper-V. For detailed info, see [[http://www.linux-kvm.org/images/0/0a/2012-forum-kvm_hyperv.pdf|Vadim's presentation from KVM Forum 2012]]. |
| |
| Windows has support for several paravirt features that it will use when running on Hyper-V, Microsoft's hypervisor. These features are called enlightenments. Many of the features are similar to paravirt functionality that exists with Linux on KVM (virtio, kvmclock, PV EOI, etc.)\\ | |
| \\ | |
| Nowadays QEMU/KVM can also enable support for several Hyper-V enlightenments. When enabled, Windows VMs running on KVM will use many of the same paravirt optimizations they would use when running on Hyper-V. For detailed info, see [[http://www.linux-kvm.org/wiki/images/0/0a/2012-forum-kvm_hyperv.pdf|Vadim's presentation]] from KVM Forum 2012.\\ | |
| \\ | |
| From the QEMU/KVM developers, the recommended configuration is: | From the QEMU/KVM developers, the recommended configuration is: |
| |
| <file>'' -cpu ...,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time '' | <code> |
| </file> | cpu ...,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time |
| \\ | </code> |
| Which maps to the libvirt XML: | Which maps to the libvirt XML: |
| | <code> |
| | <features> |
| | <hyperv> |
| | <relaxed state='on'/> // only this option is supported on Centos 6.5 KVM hypervisor |
| | <vapic state='on'/> |
| | <spinlocks state='on' retries='8191'/> |
| | </hyperv> |
| | <features/> |
| | |
| | <clock ...> |
| | <timer name='hypervclock' present='yes'/> |
| | </clock> |
| | </code> |
| |
| <file>'' <features> <hyperv> <relaxed state='on'/> <vapic state='on'/> <spinlocks state='on' retries='8191'/> </hyperv> <features/> <clock ...> <timer name='hypervclock' present='yes'/> </clock> '' | |
| </file> | |
| \\ | |
| Some details about the individual features: | Some details about the individual features: |
| |
| * relaxed/hv_relaxed. Available in libvirt 1.0.0+ ([[http://libvirt.org/git/?p=libvirt.git;a=commit;h=cc922fddc3fcbbcecce7e438a51045c2feacf767|commit]]) and qemu 1.1+ ([[http://git.qemu.org/?p=qemu.git;a=commit;h=28f52cc04d341045e810bd487a478fa9ec5f40be|commit]]). This bit disables a Windows sanity check that commonly results in a BSOD when the VM is running on a heavily loaded host (example bugs [[https://bugzilla.redhat.com/show_bug.cgi?id=1110305|here]], [[https://bugzilla.redhat.com/show_bug.cgi?id=990824|here]], and [[https://bugs.launchpad.net/ubuntu/+source/qemu/+bug/1308341|here]]). Sounds similar to the Linux kernel option no_timer_check, which is automatically enabled when Linux is running on KVM. | ^ Fetaure ^ Description ^ |
| * vapic/hv_vapic. Available in libvirt 1.1.0+ ([[http://libvirt.org/git/?p=libvirt.git;a=commit;h=19f75d5eeb6bedd49597034832284146c7591a00|commit]]) and qemu 1.1+ ([[http://git.qemu.org/?p=qemu.git;a=commit;h=28f52cc04d341045e810bd487a478fa9ec5f40be|commit]]). | |relaxed/hv_relaxed| Available in libvirt 1.0.0+ (commit) and qemu 1.1+ (commit). This bit disables a Windows sanity check that commonly results in a BSOD when the VM is running on a heavily loaded host (example bugs here, here, and here). Sounds similar to the Linux kernel option no_timer_check, which is automatically enabled when Linux is running on KVM.| |
| * spinlocks/hv_spinlocks. Available in libvirt 1.1.0+ ([[http://libvirt.org/git/?p=libvirt.git;a=commit;h=19f75d5eeb6bedd49597034832284146c7591a00|commit]]) and qemu 1.1+ ([[http://git.qemu.org/?p=qemu.git;a=commit;h=28f52cc04d341045e810bd487a478fa9ec5f40be|commit]]) | |vapic/hv_vapic| Available in libvirt 1.1.0+ (commit) and qemu 1.1+ (commit).| |
| * hypervclock/hv_time. Available in libvirt 1.2.2+ ([[http://libvirt.org/git/?p=libvirt.git;a=commit;h=600bca592b2352b683856f4b7f2694f366feac36|commit]]) and qemu 2.0+ ([[http://git.qemu.org/?p=qemu.git;a=commit;h=48a5f3bcbbbe59a3120a39106bfda59fd1933fbc|commit]]). Sounds similar to [[http://www.linux-kvm.org/page/KVMClock|kvmclock]], a paravirt time source which is used when Linux is running on KVM. | |spinlocks/hv_spinlocks| Available in libvirt 1.1.0+ (commit) and qemu 1.1+ (commit)| |
| | |hypervclock/hv_time| Available in libvirt 1.2.2+ (commit) and qemu 2.0+ (commit). Sounds similar to kvmclock, a paravirt time source which is used when Linux is running on KVM.| |
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| | It should be safe to enable these bits for all Windows VM, though only Vista/Server 2008 and later will actually make use of the features. |
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| | (In fact, Linux also has support for using these Hyper-V features, like the paravirt device drivers and hyperv_clocksource. Though these are really only for running Linux on top of Hyper-V. With Linux on KVM, the natively developed paravirt extensions are understandably preferred). |
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| | The next version of virt-manager will enable Hyper-V enlightenments when creating a Windows VM (git commit). virt-xml can also be used to enable these bits easily from the command line for an existing VM: |
| |
| \\ It should be safe to enable these bits for all Windows VM, though only Vista/Server 2008 and later will actually make use of the features. \\ \\ (In fact, Linux also has support for using these Hyper-V features, like the [[http://lwn.net/Articles/342305/|paravirt device drivers]] and hyperv_clocksource. Though these are really only for running Linux on top of Hyper-V. With Linux on KVM, the natively developed paravirt extensions are understandably preferred). \\ | <code> |
| \\ | sudo virt-xml $VMNAME --edit --features hyperv_relaxed=on,hyperv_vapic=on,hyperv_spinlocks=on,hyperv_spinlocks_retries=8191 |
| The next version of virt-manager will enable Hyper-V enlightenments when creating a Windows VM ([[https://git.fedorahosted.org/cgit/virt-manager.git/commit/?id=8ea634f9e437153a30f06b7267db2bd685af0561|git commit]]). virt-xml can also be used to enable these bits easily from the command line for an existing VM: | sudo virt-xml $VMNAME --edit --clock hypervclock_present=yes |
| | </code> |
| |
| <file>'' sudo virt-xml $VMNAME --edit --features hyperv_relaxed=on,hyperv_vapic=on,hyperv_spinlocks=on,hyperv_spinlocks_retries=8191 sudo virt-xml $VMNAME --edit --clock hypervclock_present=yes '' | |
| </file> | |
| |
| \\ The first invocation will work with virt-manager 1.0.1, the second invocation requires virt-manager.git. In my testing this didn't upset my existing Windows VMs and they worked fine after a reboot. \\ \\ Other tools aren't enabling these features yet, though there are bugs tracking this for the big ones: | The first invocation will work with virt-manager 1.0.1, the second invocation requires virt-manager.git. In my testing this didn't upset my existing Windows VMs and they worked fine after a reboot. |
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| * ovirt/vdsm: [[https://bugzilla.redhat.com/show_bug.cgi?id=1083529|https://bugzilla.redhat.com/show_bug.cgi?id=1083529]] | Other tools aren't enabling these features yet, though there are bugs tracking this for the big ones: |
| * openstack: [[https://bugzilla.redhat.com/show_bug.cgi?id=1083525|https://bugzilla.redhat.com/show_bug.cgi?id=1083525]] | |
| * gnome-boxes: [[https://bugzilla.gnome.org/show_bug.cgi?id=732811|https://bugzilla.gnome.org/show_bug.cgi?id=732811]] | |
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| (edit 2014-09-08: This change was released in [[http://blog.wikichoon.com/2014/09/virt-manager-110-released.html|virt-manager-1.1.0]]) | [[https://bugzilla.redhat.com/show_bug.cgi?id=1083529|ovirt/vdsm]] |
| | [[https://bugzilla.redhat.com/show_bug.cgi?id=1083525|openstack]] |
| | [[https://bugzilla.gnome.org/show_bug.cgi?id=732811|gnome-boxes]] |
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| | (edit 2014-09-08: This change was released in virt-manager-1.1.0) |