Bug 663418
| Summary: | [RHEL5] [XEN] - Live migration of Xen DomUs succeeds but produces error messages | ||
|---|---|---|---|
| Product: | Red Hat Enterprise Linux 5 | Reporter: | asilva <asilva> |
| Component: | xen | Assignee: | Michal Novotny <minovotn> |
| Status: | CLOSED INSUFFICIENT_DATA | QA Contact: | Virtualization Bugs <virt-bugs> |
| Severity: | medium | Docs Contact: | |
| Priority: | medium | ||
| Version: | 5.6 | CC: | areis, drjones, jmunilla, jzheng, leiwang, minovotn, mrezanin, pbonzini, qwan, xen-maint, yuzhang, yuzhou |
| Target Milestone: | rc | ||
| Target Release: | --- | ||
| Hardware: | x86_64 | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | Bug Fix | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2011-05-02 10:00:49 UTC | Type: | --- |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
| Bug Depends On: | |||
| Bug Blocks: | 699616 | ||
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Description
asilva
2010-12-15 18:13:15 UTC
Please give guest details. Was it 32-bit? What kernel release? How much memory did it have allocated to it in its config? Thanks, Drew domid (0x7ff1) isn't bogus, it's dom_io
#define DOMID_IO (0x7FF1U)
Now using it might be a bogus thing to do though...
What we know is that we went into get_page_from_l1e(), the page was present and had valid flags, but that the mfn wasn't valid, so we went into
if ( unlikely(!mfn_valid(mfn)) ||
unlikely(page_get_owner(page) == dom_io) )
{
...
d = dom_io;
}
upstream doesn't set d to dom_io for this case any more, not sense c/s 16402, which is a patch for foreign access to iomem pages. Maybe we shouldn't either?
So the error message makes sense. The pfn = 555... is the initial value for pfns ("an obvious debug pattern" per the sources). Therefore an invalid mfn could see that for the pfn and also a domid of 32753.
The remaining question is why are the mfns invalid? That question also applies to the more sane looking messages posted at the top of the description. I assume that that is because during the live migration we pulled the rug out from under a process accessing particular mfns when moving it to another machine (with different mfns assigned to it). That can be tested by live migrating a VM that isn't doing anything, or by migrating a busy machine, but not live, and then checking that the logs are clean. Perhaps when Alberto attempted to reproduce he attempted to live migrate a VM that wasn't doing anything?
Without knowing the type of guest, or what exactly it was doing at the time of migration, then it's hard to say if these error messages indicate a problem with migration or if they can be safely ignored. My understanding is that they can usually be safely ignored, because the guest kernel will generally BUG if it isn't prepared to have a failed page update.
Hello Drew,
The error is occurring without execute a live migration.
We are not able to figure out why this error occurs even if there is no live migration or guest machines in this xen host.
I've attached the host sosreport, xen dmesg and xend-config.sxp. In xen dmesg you can see the error messages.
> Perhaps when Alberto attempted to reproduce he attempted to live migrate a VM that wasn't doing anything?
A: Yes, my VM was idle during the test.
Cheers,
Alberto Silva
There is a serial console configuration on Host...it can be related? I did the tests using the same console configuration, but no errors. It may be specific to hardware. Alberto, I tried to get the machine to reproduce it but not luck. Do you have access to any machine to reproduce it now? Thanks a lot! Michal As we have enough of information on this topic and it is about warning messages, closing this bz. |