[rhelv6-list] rhel6 xenU on rhel5.5 domU - live-migrate between minor CPU revs

Rich Graves rgraves at carleton.edu
Wed Dec 1 03:45:15 UTC 2010


Under the resolved topic "rhel6 xenU on rhel5.5 domU - no console," "Pasi Kärkkäinen" <pasik at iki.fi> asked:

> Did you file a bugzilla entry about the live migration issue? 

Still no, but I might have the answer. I just don't like it.

My DNS/network issues were a red herring, caused a bug in our McAfee/Sidewinder firewall. RHEL6 sends back-to-back A and AAAA queries in separate packets, and the Sidewinder's DNS proxy only passes the former. Other OSes either send two queries in one packet or don't send them back-to-back with sequential TXIDs. However, one real problem with Xen live-migrate remains.

It could be due to processor flags. I can fairly consistently migrate a guest from a X5680 processor (Nehalem2 Westmere) to a L5520 (original Nehalem), and usually from a 5160 (Core2 Duo) to a 5060 (Core Duo), but not the other way around.

In contrast, all of my RHEL4 and RHEL5 guests are able to move *anywhere*, even between the 5060 and 5680, as long as basic things like NX are set the same in BIOS. Maybe the problem is that the newer RHEL6 kernel is too smart for its own good? Can I mask the newest flags somehow?

The processor flags are:

X5680
flags           : fpu tsc msr pae cx8 apic mtrr cmov pat clflush acpi mmx fxsr sse sse2 ss ht syscall nx lm constant_tsc ida arat pni est ssse3 cx16 sse4_1 sse4_2 popcnt lahf_lm

X5520
flags           : fpu tsc msr pae cx8 apic mtrr cmov pat clflush acpi mmx fxsr sse sse2 ss ht syscall nx lm constant_tsc ida pni est ssse3 cx16 sse4_1 sse4_2 popcnt lahf_lm

5060
flags           : fpu tsc msr pae cx8 apic mtrr cmov pat clflush acpi mmx fxsr sse sse2 ss ht syscall nx lm constant_tsc pni cid cx16 lahf_lm

5160
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc pni monitor ds_cpl est tm2 xtpr
-- 
Rich Graves http://claimid.com/rcgraves
Carleton.edu Sr UNIX and Security Admin
CMC135: 507-222-7079 Cell: 952-292-6529




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