On Tue, Nov 30, 2010 at 09:45:15PM -0600, Rich Graves wrote:
> Under the resolved topic "rhel6 xenU on rhel5.5 domU - no console," "Pasi 
> Kärkkäinen" <[email protected]> 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
>

Xen has support for cpuid masking, but I'm not sure if EL5 Xen has that..
ie. it's at least in newer Xen versions.

-- Pasi

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