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

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

Jan Beulich wrote on 2011-12-21:
>>>> On 21.12.11 at 12:22, "Wei, Gang" <gang.wei@xxxxxxxxx> wrote:
>> Without this delay, Xen could not bring APs up while working with
>> TXT/tboot, because tboot need some time in APs to handle INIT before
>> becoming ready for receiving SIPIs. (this delay was removed as part
>> of c/s 23724 by Tim Deegan)
>> 
>> Signed-off-by: Gang Wei <gang.wei@xxxxxxxxx>
>> 
>> diff -r d1aefee43af1 xen/arch/x86/smpboot.c
>> --- a/xen/arch/x86/smpboot.c    Wed Dec 21 18:51:31 2011 +0800
>> +++ b/xen/arch/x86/smpboot.c    Wed Dec 21 19:08:57 2011 +0800
>> @@ -463,6 +463,10 @@ static int wakeup_secondary_cpu(int phys
>>              send_status = apic_read(APIC_ICR) & APIC_ICR_BUSY;
>>          } while ( send_status && (timeout++ < 1000) );
>>      }
>> +    else
>> +    {
>> +        mdelay(10);
>> +    }
> 
> Does it really need to be this long then (even in the non-TBOOT case)?

No, it could be shorter. I just take a used value back here. If it does matter, 
we could use a tested working value here: udelay(10), and for tboot case only.

Jimmy

> 
> Jan
> 
>> 
>>      /*
>>       * Should we send STARTUP IPIs ?
> 
>

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