Bug 1053847
| Summary: | Recommended default clock/timer settings | ||
|---|---|---|---|
| Product: | [Community] Virtualization Tools | Reporter: | Cole Robinson <crobinso> |
| Component: | libguestfs | Assignee: | Richard W.M. Jones <rjones> |
| Status: | CLOSED CURRENTRELEASE | QA Contact: | |
| Severity: | unspecified | Docs Contact: | |
| Priority: | unspecified | ||
| Version: | unspecified | CC: | mbooth, ptoscano, rjones |
| Target Milestone: | --- | ||
| Target Release: | --- | ||
| Hardware: | Unspecified | ||
| OS: | Unspecified | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | Bug Fix | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2018-10-09 14:44:04 UTC | Type: | Bug |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
I've long suspected that libguestfs is doing the wrong thing. Pino? (In reply to Cole Robinson from comment #0) > Recently there was an internal discussion with several qemu developers about > default VM clock/timer configuration. What they recommended maps to this > libvirt XML: > > <clock ...> > <timer name="rtc" tickpolicy="catchup"/> > <timer name="pit" tickpolicy="delay"/> > <timer name="hpet" present="no"/> > </clock> > > This maps to the qemu command line options: > > -rtc driftfix=slew -no-hpet -no-kvm-pit-reinjection > > Explicitly this was recommended for all guest OS. Some bits don't affect > certain OS, but in those cases they are harmless. Easy enough to change. From a quick test here, using - libvirt 1.0.5.8-1.fc19.x86_64 - qemu-kvm 1.4.2-15.fc19.x86_64 I see in libvirt's log: -rtc base=utc,driftfix=slew -no-kvm-pit-reinjection -no-hpet (we pass <clock offset="utc">, hence "base=utc"), so should be working. Is there any minimum combination of libvirt and/or qemu for the options above to work? Currently we require: - qemu >= 1.1 (although 1.2 is strongly recommeded) - libvirt >= 0.10.2 > Libguestfs is currently only adding: > > <timer name="kvmclock" present="yes"/> > > This is actually non-functional with qemu AFAICT from inspecting the code: > if kvm is enabled, kvmclock is enabled by default. if kvm is not enabled, > kvmclock will never be enabled, even if the user requests it. So trying to > force it on the command line has no effect (maybe it did in older qemu > versions). Not useful indeed. (In reply to Pino Toscano from comment #2) > (In reply to Cole Robinson from comment #0) > > Recently there was an internal discussion with several qemu developers about > > default VM clock/timer configuration. What they recommended maps to this > > libvirt XML: > > > > <clock ...> > > <timer name="rtc" tickpolicy="catchup"/> > > <timer name="pit" tickpolicy="delay"/> > > <timer name="hpet" present="no"/> > > </clock> > > > > This maps to the qemu command line options: > > > > -rtc driftfix=slew -no-hpet -no-kvm-pit-reinjection > > > > Explicitly this was recommended for all guest OS. Some bits don't affect > > certain OS, but in those cases they are harmless. > > Easy enough to change. From a quick test here, using > - libvirt 1.0.5.8-1.fc19.x86_64 > - qemu-kvm 1.4.2-15.fc19.x86_64 > I see in libvirt's log: > -rtc base=utc,driftfix=slew -no-kvm-pit-reinjection -no-hpet > (we pass <clock offset="utc">, hence "base=utc"), so should be working. > > Is there any minimum combination of libvirt and/or qemu for the options > above to work? Currently we require: > - qemu >= 1.1 (although 1.2 is strongly recommeded) > - libvirt >= 0.10.2 I see the timer XML changes went into libvirt in 2010, which is before 0.10.2. So I think those checks should be sufficient. I'm going to make the minimum version of libvirt be 1.1.1 (since that is the version we will ship in RHEL 7.0). https://github.com/libguestfs/libguestfs/commit/6b3e05e8da490fc11a2f07f0cc9022216a744ac7 I've fixed this as a side-effect of cleaning up some libguestfs backend code. Will post a patch shortly. Fixed in https://github.com/libguestfs/libguestfs/commit/b6ff6421686e6fd7e5f7db8eed24419c7bd09688 As we should probably backport this to earlier branches, leaving this bug open for now. FYI, qemu now prints out this warning: Warning: option deprecated, use lost_tick_policy property of kvm-pit instead. I assume it's talking about -no-kvm-pit-reinjection. Yeah I believe upstream libvirt has a fix to use the new option, or at least there was a patch posted once Thanks .. Seems to be this one: http://libvirt.org/git/?p=libvirt.git;a=commitdiff;h=1569fa14d8f6b6636cf78d7ee62ae3bd205f5638 The new option would appear to be: -global kvm-pit.lost_tick_policy=discard I've posted a patch for libguestfs: https://www.redhat.com/archives/libguestfs/2014-January/msg00216.html |
Recently there was an internal discussion with several qemu developers about default VM clock/timer configuration. What they recommended maps to this libvirt XML: <clock ...> <timer name="rtc" tickpolicy="catchup"/> <timer name="pit" tickpolicy="delay"/> <timer name="hpet" present="no"/> </clock> This maps to the qemu command line options: -rtc driftfix=slew -no-hpet -no-kvm-pit-reinjection Explicitly this was recommended for all guest OS. Some bits don't affect certain OS, but in those cases they are harmless. Libguestfs is currently only adding: <timer name="kvmclock" present="yes"/> This is actually non-functional with qemu AFAICT from inspecting the code: if kvm is enabled, kvmclock is enabled by default. if kvm is not enabled, kvmclock will never be enabled, even if the user requests it. So trying to force it on the command line has no effect (maybe it did in older qemu versions).