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June 2014

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[libvirt] [PATCHv2 0/4] qemu: fix broken RTC_CHANGE event when clock offset='variable'
by Laine Stump 31 May '14

31 May '14

(the cover letter from V1 has been preserved here with small updates) This patch series is all about: https://bugzilla.redhat.com/show_bug.cgi?id=964177 which points out a flaw in qemu's RTC_CHANGE event when the base for the guest's real time clock was given as an explicit date (rather than as 'utc' or 'localtime'). Patch 3/4 explains what qemu does, and how this patch fixes it (for the case of basis='utc' - an additional fix to properly support basis='localtime', both for RTC_CHANGE and when migrating across timezone/DST boundaries, is in Patch 4/4). (NB: the flawed RTC_CHANGE offset has been in QEMU for so long now that it has been documented and cannot be changed, so libvirt must work around it) In the meantime, the fix for basis='localtime' required that we learn the offset of localtime from utc, and that seems like something we might want to do for other reasons, so Patch 1/4 adds a new utility function do get that value that is (I hope!) POSIX compliant. Since the original patch to fix this problem was incorrect, and the new patch doesn't use any of its code, Patch 2/4 reverts that patch completely. Note that I have tested this patch by starting a domain with several variations of <clock> parameters (in a locale that is currently at UTC+3) and using the following short script to add and remove seconds from the guest's RTC while watching both the <clock> line in /var/run/libvirt/qemu/$domain.xml and the offset value sent in libvirt's VIR_DOMAIN_EVENT_ID_RTC_CHANGE event (using examples/domain-events/events-c/event-test from a libvirt source tree that has been built). All cases appear to maintain the adjustment in the status properly, as well as sending the correct value to any event handler. Here is the script I used to add/remove time from the RTC: #!/bin/sh old=$(hwclock --show | cut -f1-7 -d' ') oldabs=$(date +%s --date="$old") newabs=$(expr $oldabs + $1) new=$(date --date="@$newabs") echo Old: $oldabs $old echo New: $newabs $new hwclock --set --date="@$newabs" Laine Stump (4): util: new function virTimeLocalOffsetFromUTC Revert "qemu: Report the offset from host UTC for RTC_CHANGE event" qemu: fix RTC_CHANGE event for <clock offset='variable' basis='utc'/> qemu: fix <clock offset='variable' basis='localtime'/> src/conf/domain_conf.c | 32 +++++++++++++------------------- src/conf/domain_conf.h | 8 +++++--- src/libvirt_private.syms | 1 + src/qemu/qemu_command.c | 43 ++++++++++++++++++++++++++++++------------- src/qemu/qemu_process.c | 34 +++++++++++++++++++--------------- src/util/virtime.c | 41 ++++++++++++++++++++++++++++++++++++++++- src/util/virtime.h | 5 +++-- tests/virtimetest.c | 44 ++++++++++++++++++++++++++++++++++++++++++++ 8 files changed, 155 insertions(+), 53 deletions(-) -- 1.9.0

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