[PATCH] PPC: Don't sync timebase when inside VM

[McClintock Matthew-B29882]

On Thu, Mar 8, 2012 at 12:20 PM, Scott Wood <scottwood at freescale.com> wrote:
> On 03/08/2012 11:31 AM, McClintock Matthew-B29882 wrote:
>> On Fri, Mar 2, 2012 at 11:17 AM, Scott Wood <scottwood at freescale.com> wrote:
>>> On 03/02/2012 10:30 AM, Alexander Graf wrote:
>>>>
>>>> On 02.03.2012, at 17:20, Scott Wood wrote:
>>>>> Again, for 85xx we should *never* sync the timebase in the kernel,
>>>>> hypervisor or no.
>>>>
>>>> The code says "if the kexec config option is enabled, do the sync". I'm fairly sure it's there for a reason.
>>>
>>> Sigh.  I forgot about that.  It's because instead of doing kexec the
>>> simple way, we actually physically reset the core.  We really shouldn't
>>> do that.  And we *really* shouldn't do it just because CONFIG_KEXEC is
>>> defined, regardless of whether we're actually booting from kexec.
>>
>> How would one rocver a core that's off in the weeds?
>
> System reset?

kdump restarts a kernel using a reserved memory region to inspect the
memory of the crashed kernel. Wouldn't system reset cause issues here?

> I thought kexec was for upgrading your kernel, not recovering from crashes.
>
>> We need to at least stop it somehow before we restart into the kdump kernel. kexec
>> seems feasible since we have all the cores in a known state...
>
> Stop, yes.  Reset, no.

How would we stop the remaining cores assuming they could be in any state?

-M