On Thu, May 9, 2019 at 7:43 PM Daniel Henrique Barboza <danielhb413@xxxxxxxxx> wrote: > > This is a VM with 'osxsave' capability declared, when there is no > 'osxsave' guest support, using this series on top of current master: > > > $ sudo ./run tools/virsh start ub1810-osxsave > error: Failed to start domain ub1810-osxsave > error: internal error: process exited while connecting to monitor: 2019-05-09T17:10:41.077568Z qemu-system-x86_64: can't apply global Skylake-Client-IBRS-x86_64-cpu.osxsave=off: Property '.osxsave' not found > > > Applying this series makes the VM boot up, as intended. > > I believe there is room for discussion whether the VM should boot > up or fail to boot with a "feature not found" error like the case below, > in a sense of "you can't disable a feature that does not exist": > > <feature policy='disable' name='not_a_cap'/> > > $ sudo ./run tools/virsh start ub1810-unknown-cap > error: Failed to start domain ub1810-unknown-cap > error: unsupported configuration: unknown CPU feature: not_a_cap > > But the alternative presented in this series does the trick and it's > less annoying for existing VMs. > > > For all the patch series: > > > Reviewed-by: Daniel Henrique Barboza <danielhb413@xxxxxxxxx> > Tested-by: Daniel Henrique Barboza <danielhb413@xxxxxxxxx> Thank you so much Daniel! Anyone else to chime in? Otherwise, having review and a test not done by me, I feel complete and would I'd like to push this later this week. > > On 4/25/19 9:50 AM, Christian Ehrhardt wrote: > > Hi, > this series tries to address a drop of commandline options by qemu in regard to > osxsave [1] and ospke [2]. > This was already discussed in [3] late last year but got forgotten afterwards. > The Ubuntu bug is at [4] and an older Fedora bug is at [5]. > > TL;DR: > - osxsave/ospke features were never really configurable > - KVM never returned the bits on GET_SUPPORTED_CPUID > - very rare to be seen in the wild > - avoid issues with newer qemu and old/odd XMLs to be sure > > Details: > > I checked various use cases from virt-install to openstack and some in between. > The only cases I found that would define osxsave/ospke is virt-install pior > to version 2.0 and even there only when used with --cpu=host-model or > --cpu=host-copy. > If you ever really enabled the feature you'd have got: > error: the CPU is incompatible with host CPU: > Host CPU does not provide required features: ospke > > The problem lies in domain XMLs that explicitly disable it. That would be > <feature policy='disable' name='osxsave'/> > But due to almost (or actually none) no host exposing this the following > also triggers: > <feature policy='optional' name='ospke'/> > > This will make libvirt add it to the qemu commandline like: > -cpu ...,osxsave=off,ospke=off > > And that will crash when qemu starts with: > error: internal error: process exited while connecting to monitor: > 2019-04-25T12:12:01.698646Z qemu-system-x86_64: can't apply global > core2duo-x86_64-cpu.osxsave=off: Property '.osxsave' not found > > There are much more long term discussions about demoting and dropping qemu > features and I'd like to avoid those discussions being mixed. > The reason to drop it more or less without notice was that it never did > anything to begin with. Due to that our solution might in a similar fashion > be more trivial - just stop defining those two features to qemu commandline. > > [1]: https://git.qemu.org/?p=qemu.git;a=commit;h=f1a23522b03a569f13aad49294bb4c4b1a9500c7 > [2]: https://git.qemu.org/?p=qemu.git;a=commit;h=9ccb9784b57804f5c74434ad6ccb66650a015ffc > [3]: https://www.mail-archive.com/qemu-devel@xxxxxxxxxx/msg561877.html > [4]: https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1825195 > [5]: https://bugzilla.redhat.com/show_bug.cgi?id=1644848 > > Christian Ehrhardt (2): > qemu: do not define known no-op features > qemuxml2argvtest: add test for remove cpu features > > src/qemu/qemu_command.c | 23 +++++++++++++++ > .../qemuxml2argvdata/cpu-host-model-cmt.args | 2 +- > .../cpu-no-removed-features.args | 29 +++++++++++++++++++ > .../cpu-no-removed-features.xml | 23 +++++++++++++++ > tests/qemuxml2argvdata/cpu-tsc-frequency.args | 4 +-- > tests/qemuxml2argvtest.c | 1 + > 6 files changed, 79 insertions(+), 3 deletions(-) > create mode 100644 tests/qemuxml2argvdata/cpu-no-removed-features.args > create mode 100644 tests/qemuxml2argvdata/cpu-no-removed-features.xml > > -- Christian Ehrhardt Software Engineer, Ubuntu Server Canonical Ltd -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
