[PATCH] powerpc/85xx: disable timebase synchronization under the hypervisor
timur at freescale.com
Fri Jun 24 03:33:40 EST 2011
Scott Wood wrote:
> From Power ISA 2.06B, book III-E, section 9.2.1:
> Virtualized Implementation Note:
> In virtualized implementations, TBU and TBL are
But does that mean that a guest should never be allowed to modify a virtualized
timebase register, even if the hypervisor can support it?
>> > So a generic HV mode bit is not going to help me, unless there's also a bit
>> > that's specific to our hypervisor. And even then, we would need some way to
>> > differentiate among different versions of our hypervisor, in case some future
>> > version adds timebase support.
> That's very unlikely to happen.
I know. I was just being architecturally pedantic.
> Ideally we would avoid doing this sync even when not running under a
> hypervisor, as long as firmware has done the sync, and kexec hasn't messed
> it up. Besides being a waste of boot time, the firmware's sync is
> probably tighter since it can use a platform-specific mechanism to start all
> the timebases at once.
I agree with that, but for now, I need to work around that kexec "limitation".
Linux kernel developer at Freescale
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