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

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

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

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