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Re: [Xen-devel] Migration and CPU type?

Noam Taich wrote:
I created my guest on my Athlon and tried to migrate it to my laptop 
running a Pentium M. The guest failed.
As a general principle, migrating between AMD and Pentium chipsets is a bad idea.
If you google a bit, VMware has VMotion compatibility tables that match 
which processor families they consider "safe" to migrate to and from.
Regards,

Anthony Liguori
When I tried the opposite, creating it on my laptop and migrating it 
to my Athlon, it worked… Not only that, but now, after being forged in 
the flamed of the Pentium M, I could migrate it BACK from the Athlon 
to the laptop…then to an Opteron… That was fun. It can actually 
function like a roaming guestJ
One problem is that OSs usually gather information on the system they 
are running, on all the features the CPU offers them.
What if one or more of the features is not supported on the target 
host? You think it will crash?
NOT necessarily. It won't crash if there's currently no running code 
on the guest that uses that feature.
I believe It will also be a problem if some code that USES such a 
feature is ON the guest RAM image, but for some reason is not
Currently running, until a user dose something…this could lead to 
seemingly unexplained crashes.
I am also interested in future compilations/executions on the migrated OS…

It can be affected too…

NOW, having said that… completely preventing migration between CPUS that are not 100% compatible may not be a good idea… after all…you may KNOW that the current configuration will work on the other machine (or you may know it was migrated from there
In the first place), and you may need to do a hardware upgrade with no 
downtime… no reason to prevent this…
I discovered that as long as you create the guest on the machine with 
the LEAST amount of features among the ones it may
Be migrated to (the one that has NO feature the other ones don't have) 
, the migration seems to work fine in every direction.
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