Re: [Xen-devel] [patch] x86: Add a delay between INIT & SIPIs for tboot AP bring-up in X2APIC case

["Wei, Gang" <gang.wei@xxxxxxxxx>]

Tim Deegan wrote on 2011-12-27:
> At 10:05 +0000 on 27 Dec (1324980346), Wei, Gang wrote:
>>> So you jumped from 100ms to 10us - how was that value established?
>>> Or in other words, how certain is it that this (or any other)
>>> timeout is sufficient for all current and future systems implementing tboot?
>> 
>> First way, code analysis. Tboot VMExitHandler only judge the
>> condition, enable trapping SIPI, then VMResume. 10us means more than
>> 10,000 cycles in Intel processors supporting TXT, it should be
>> enough for this simple code path.
> 
> Unless the BIOS does clever things in SMM of course. :)

If no further question on this patch from anyone else, could you help to check 
it in?

> 
>> Further, I am working on changing the SMP bring-up sequence for
>> tboot path from INIT-SIPI-SIPI to MWAIT-memwrite style. It means
>> tboot APs will wait in MWAIT loops and Xen BSP will try to write the
>> monitored memory to bring APs out of MWAIT loops.
> 
> That sounds like a very good idea.

I will send out the patch for MWAIT SMP bring-up soon.

Jimmy

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