kGraft — live kernel patching from SUSE

Posted Feb 4, 2014 4:10 UTC (Tue) by joyuh (guest, #95216)
In reply to: kGraft — live kernel patching from SUSE by jhhaller
Parent article: kGraft — live kernel patching from SUSE

You can just use live migration to migrate a VM to a new version of QEMU.

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kGraft — live kernel patching from SUSE

Posted Feb 4, 2014 8:56 UTC (Tue) by pbonzini (subscriber, #60935) [Link] (4 responses)

That doesn't help with upgrading the kernel inside the VM.

kGraft — live kernel patching from SUSE

Posted Feb 4, 2014 9:54 UTC (Tue) by dgm (subscriber, #49227) [Link] (3 responses)

You could use something like LinuxPMI or OpenMOSIX to migrate processes to the new kernel.

In fact, an alternative method to update the kernel would be to boot a second kernel and migrate processes to it using this mechanism.

Maybe one day.

kGraft — live kernel patching from SUSE

Posted Feb 4, 2014 13:37 UTC (Tue) by ledow (guest, #11753) [Link] (2 responses)

So long as you don't mind using 2.6 kernels and/or not having 9 things that a process could do that might stop it migrating (such as using I/O directly, having a memory-mapped file, etc.).

There's plenty of reasons that something like ksplice would be superior under certain workloads than trying to revive a (dead) concept / software project.

kGraft — live kernel patching from SUSE

Posted Feb 4, 2014 22:11 UTC (Tue) by dgm (subscriber, #49227) [Link]

There are hurdles to doing it right now, but no fatal flaws in the concept. ksplice may be "superior under certain workloads", but process migration is a good design idea that will be implemented anyway on the long term.

kGraft — live kernel patching from SUSE

Posted Feb 6, 2014 17:54 UTC (Thu) by cov (guest, #84351) [Link]

CRIU can do this and is very much alive.

kGraft — live kernel patching from SUSE

Posted Feb 4, 2014 14:22 UTC (Tue) by jhhaller (guest, #56103) [Link]

Live migration has its limits, including a short period of time between when the VM stops on the old host, the last few memory updates are forwarded to the new host, and the VM starts again. For some applications, that time may be long enough to be considered downtime, even if it's a fraction of a second. Those are the applications which benefit from live patching and reduction in the number of events where software must be updated.