On 09/04/2013 09:54 PM, Benjamin Herrenschmidt wrote: > On Wed, 2013-09-04 at 21:40 +1000, Alexey Kardashevskiy wrote: >> One of the examples (came from Paul) is: >> the host runs on POWER8, the guest boots a kernel which is capable of >> POWER7 only + POWER7-compat. We do this reboot tweak and boot in >> POWER7-compat mode. Then the guest does "yum update" and gets POWER8 >> kernel >> installed so when it reboots, it will boot in normal POWER8 mode. >> Everybody >> is happy. >> >> Having POWER7-compat mode set from the very beginning will break this >> behaviour. > > But it will allow migrating that partition to a P7 machine. It's > important to be able to specify the compat mode for that reason, to > create guests that can be migrated to older machines.
I am not saying we do not need this feature, I am saying we do not always want it. -- Alexey
