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

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

Tim Deegan wrote on 2011-12-22:
>> Second, with tboot AP is actually spinning in a mini-guest before
>> receiving INIT, upon receiving INIT ipi, AP need time to VMExit,
>> update VMCS to tracking SIPIs and VMResume. After that SIPI is able
>> to be trapped by APs. This is MUST if giving no change to current AP
>> bring-up method(INIT-SIPI-SIPI) for tboot.
> 
> Oh I see - and the CPU blocks SIPIs in root mode; how inconvenient.
> Does tboot also need a delay between the two SIPIs then?

No. Tboot actually skip the second SIPI.

>> I have provided a resent patch with code comment in a previous reply.
> 
> Your comment should say _why_ -- in particular that while tboot is in
> root mode handling the INIT the CPU will drop any SIPIs.

Ok, I will add more words and resend it again.

> With that change, Ack.
> 
> Tim.

Jimmy

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