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

[Keir Fraser <keir@xxxxxxx>]

Please add a code comment explaining why the delay is needed. Apart from
that:

Acked-by: Keir Fraser <keir@xxxxxxx>


On 21/12/2011 12:29, "Wei, Gang" <gang.wei@xxxxxxxxx> wrote:

> Resent:
> 
> 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)
> 
> 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 20:26:39 2011 +0800
> @@ -42,6 +42,7 @@
>  #include <asm/msr.h>
>  #include <asm/mtrr.h>
>  #include <asm/time.h>
> +#include <asm/tboot.h>
>  #include <mach_apic.h>
>  #include <mach_wakecpu.h>
>  #include <smpboot_hooks.h>
> @@ -463,6 +464,10 @@ static int wakeup_secondary_cpu(int phys
>              send_status = apic_read(APIC_ICR) & APIC_ICR_BUSY;
>          } while ( send_status && (timeout++ < 1000) );
>      }
> +    else if ( tboot_in_measured_env() )
> +    {
> +        udelay(10);
> +    }
> 
>      /*
>       * Should we send STARTUP IPIs ?
> 
> Jimmy
> 
> 
>> -----Original Message-----
>> From: Wei, Gang
>> Sent: Wednesday, December 21, 2011 8:18 PM
>> To: Keir Fraser; xen-devel@xxxxxxxxxxxxxxxxxxx
>> Cc: tboot-devel@xxxxxxxxxxxxxxxxxxxxx; Jan Beulich; Tim Deegan; Cihula,
>> Joseph; Wei, Gang
>> Subject: RE: [patch] x86: Add a delay between INIT & SIPIs for AP bring-up in
>> X2APIC case
>> 
>> Keir Fraser wrote on 2011-12-21:
>>> On 21/12/2011 11:22, "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)
>>> 
>>> Of course Tim will need to review this himself, but a mdelay() right
>>> here, only on the x2apic path just looks bizarre and fragile.
>>> 
>>> Could we make the !x2apic_enabled conditionals that Tim added be
>>> !(x2apic_enabled || tboot_in_measured_env()) instead? At least that is
>>> somewhat self-documenting and clearly only affects tboot!
>> 
>> Does below patch make more sense?
>> 
>> 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 if ( tboot_in_measured_env() )
>> +    {
>> +        udelay(10);
>> +    }
>> 
>>      /*
>>       * Should we send STARTUP IPIs ?
>> 
>> Jimmy



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel