Re: Re: system freeze when processor.ko is loaded

[Keir Fraser <keir.xen@gmail.com>]

On 12/04/2011 18:27, "Wang, Winston L" <winston.l.wang@intel.com> wrote:

>>>>> On 12.04.11 at 00:35, "Wang, Winston L" <winston.l.wang@intel.com>
>> wrote:
>>> I think restore only the lower 32bit TSC is good enough, why do we
>> need to touch upper 32 bit TSC?
>> 
>> You just can't: A wrmsr to this MSR always updates the full 64-bits,
>> just that on some CPUs this update implies the upper 32 bits getting
>> zeroed.
> You are right, just can't only write lower 32 bit without updating 32 bit
> since TSC is always 64 bits:(
> So we have to give up the deep C state for those old processors since we still
> need to maintain TSC all the time for SMP support.
> The solution should go with your patch: re-validate the processor boot with "
> X86_FEATURE_TSC_RELIABLE" to see upper 32 bit TSC MSR is writeable at
> init_xen_time or not , then decide if allow deep_cstate. This is a better idea
> than only allow the processor going to the deep c state with
> "x86_FEATURE_CONSTANT_TSC but !X86_FEATURE_NONSTOP_TSC CPUs".
> 
> Would you double test patch before pulling in? we need to check both the old
> failed processor and the current one. And what's the power idle power impact.

Do you want a chance to Ack the patch before I apply it to xen-unstable?

 -- Keir

>> And even if you could, it wouldn't be easy to deal with the situation
>> where the update would carry into the upper 32 bits.
>> 
>> Jan
>> 
>>> 1. I would not think if any processor's deep c-state wakeup from idle
>> can
>>> more than 100 ms.
>>> 2. For 3GHZ processor lower 32bit TSC wrapper around time is ~2.83
>> Sec.
>>> 3. The platform timer (22bit ACPI timer) wrapper around is 2.34 sec
>> (this is
>>> used for counting the delta before enter deep_cstate and before
>> wakeup)
>>> Just need to change cstate_restore_tsc() and only patch back the
>> delta time
>>> to the lower 32 bit TSC to make that simple?
>>> 
>>> Winston,
>> 
>> 
>