RHEL Engineering is moving the tracking of its product development work on RHEL 6 through RHEL 9 to Red Hat Jira (issues.redhat.com). If you're a Red Hat customer, please continue to file support cases via the Red Hat customer portal. If you're not, please head to the "RHEL project" in Red Hat Jira and file new tickets here. Individual Bugzilla bugs in the statuses "NEW", "ASSIGNED", and "POST" are being migrated throughout September 2023. Bugs of Red Hat partners with an assigned Engineering Partner Manager (EPM) are migrated in late September as per pre-agreed dates. Bugs against components "kernel", "kernel-rt", and "kpatch" are only migrated if still in "NEW" or "ASSIGNED". If you cannot log in to RH Jira, please consult article #7032570. That failing, please send an e-mail to the RH Jira admins at rh-issues@redhat.com to troubleshoot your issue as a user management inquiry. The email creates a ServiceNow ticket with Red Hat. Individual Bugzilla bugs that are migrated will be moved to status "CLOSED", resolution "MIGRATED", and set with "MigratedToJIRA" in "Keywords". The link to the successor Jira issue will be found under "Links", have a little "two-footprint" icon next to it, and direct you to the "RHEL project" in Red Hat Jira (issue links are of type "https://issues.redhat.com/browse/RHEL-XXXX", where "X" is a digit). This same link will be available in a blue banner at the top of the page informing you that that bug has been migrated.
Bug 589963 - Time jump backwards in Guest r3u9-32
Summary: Time jump backwards in Guest r3u9-32
Keywords:
Status: CLOSED WORKSFORME
Alias: None
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: qemu-kvm
Version: 6.0
Hardware: All
OS: Linux
urgent
medium
Target Milestone: rc
: ---
Assignee: Zachary Amsden
QA Contact: Virtualization Bugs
URL:
Whiteboard:
Depends On:
Blocks: 528898
TreeView+ depends on / blocked
 
Reported: 2010-05-07 12:15 UTC by Golita Yue
Modified: 2013-01-11 02:58 UTC (History)
21 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of: 570824
Environment:
Last Closed: 2010-06-08 00:16:01 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)
clock test (596 bytes, text/x-csrc)
2010-05-07 12:20 UTC, Golita Yue 		no flags Details
result of r3u9-32 (11.75 KB, text/plain)
2010-05-07 12:21 UTC, Golita Yue 		no flags Details
View All

Comment 1 Golita Yue 2010-05-07 12:20:29 UTC 
Created attachment 412325 [details]
clock test
Comment 2 Golita Yue 2010-05-07 12:21:36 UTC 
Created attachment 412326 [details]
result of r3u9-32
Comment 4 RHEL Program Management 2010-05-07 14:08:15 UTC 
This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux major release.  Product Management has requested further
review of this request by Red Hat Engineering, for potential inclusion in a Red
Hat Enterprise Linux Major release.  This request is not yet committed for
inclusion.
Comment 6 Dor Laor 2010-05-09 11:28:19 UTC 
Please provide the qemu cmdline parameters and kvm/kernel versions.
Note that in 3.9 there is no pvclock, it's probably only the PIT.
Comment 8 Dor Laor 2010-05-11 08:12:21 UTC 
Do you run anything special in the guest? NTP? Do any action like migration?
I find it pretty weird that the time goes backward for standard run.
Comment 10 Zachary Amsden 2010-05-11 22:59:55 UTC 
Well, my 3.9 guest was using HPET, but that wasn't RHEL5.  Since you're disabling HPET in the command line, the guest should probably end up using the dreaded TSC.

Can you strip -no-hpet from the options?  I'm not sure if we officially support HPET for RHEL5, but the choice here is either fix the TSC or support the HPET.
Comment 11 Dor Laor 2010-05-11 23:21:05 UTC 
hpet is not supported, I thought rhel3 uses the PIT, better add notsc cmdline to it
Comment 13 Zachary Amsden 2010-05-12 05:31:39 UTC 
So that's PIT timer jumping backwards?  Yikes.
Comment 14 Zachary Amsden 2010-05-12 05:34:32 UTC 
Actually, can you post results from:

dmesg | grep -i time

It would be nice to confirm the PIT is really being used.  Very strange the jiffies clock would cause backwards time or be any different on SMP.

Are you sure there is no ntpd / ntpdate running?
Comment 15 Zachary Amsden 2010-06-08 00:16:01 UTC 
This bug is too confused to really make sense of.  There are multiple guests running different versions of RHEL mentioned.  I'm hopefully that Glauber's fixes and fixes to the various tick compensation mechanisms have already successfully resolved this bug.  In any case, local testing hasn't shown unstable time in r3u9 guests - and if it's TSC compensation which is causing the problem, there is already another open bug for that which is assigned to me.
Note You need to log in before you can comment on or make changes to this bug.