Re: [PATCH] KEXEC: disable hpet legacy broadcasts earlier

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 18/08/11 14:47, Keir Fraser wrote:
> On 18/08/2011 14:31, "Andrew Cooper" <andrew.cooper3@citrix.com> wrote:
>
>> On x2apic machines which booted in xapic mode,
>> hpet_disable_legacy_broadcast() sends an event check IPI to all online
>> processors.  This leads to a protection fault as the genapic blindly
>> pokes x2apic MSRs while the local apic is in xapic mode.
>>
>> One option is to change genapic when we shut down the local apic, but
>> there are still problems with trying to IPI processors in the online
>> processor map which are actually sitting in NMI loops
>>
>> Another option is to have each CPU take itself out of the online CPU
>> map during the NMI shootdown.
>>
>> Realistically however, disabling hpet legacy broadcasts earlier in the
>> kexec path is the easiest fix to the problem.
> This for 4.1.2 as well I guess?

Yes please

~Andrew

>> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
>>
>> diff -r fc2be6cb89ad -r dcb3ed7b7dbd xen/arch/x86/crash.c
>> --- a/xen/arch/x86/crash.c Tue Aug 16 15:05:55 2011 +0100
>> +++ b/xen/arch/x86/crash.c Thu Aug 18 14:30:32 2011 +0100
>> @@ -29,6 +29,7 @@
>>  #include <asm/io_apic.h>
>>  #include <xen/iommu.h>
>>  #include <xen/pci.h>
>> +#include <asm/hpet.h>
>>  
>>  static atomic_t waiting_for_crash_ipi;
>>  static unsigned int crashing_cpu;
>> @@ -61,6 +62,9 @@ static void nmi_shootdown_cpus(void)
>>  
>>      local_irq_disable();
>>  
>> +    if ( hpet_broadcast_is_available() )
>> +        hpet_disable_legacy_broadcast();
>> +
>>      crashing_cpu = smp_processor_id();
>>      local_irq_count(crashing_cpu) = 0;
>>  
>> diff -r fc2be6cb89ad -r dcb3ed7b7dbd xen/arch/x86/machine_kexec.c
>> --- a/xen/arch/x86/machine_kexec.c Tue Aug 16 15:05:55 2011 +0100
>> +++ b/xen/arch/x86/machine_kexec.c Thu Aug 18 14:30:32 2011 +0100
>> @@ -85,9 +85,6 @@ void machine_kexec(xen_kexec_image_t *im
>>          .limit = LAST_RESERVED_GDT_BYTE
>>      };
>>  
>> -    if ( hpet_broadcast_is_available() )
>> -        hpet_disable_legacy_broadcast();
>> -
>>      /* We are about to permenantly jump out of the Xen context into the kexec
>>       * purgatory code.  We really dont want to be still servicing interupts.
>>       */
>>
>> _______________________________________________
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>> Xen-devel@lists.xensource.com
>> http://lists.xensource.com/xen-devel
>

-- 
Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer
T: +44 (0)1223 225 900, http://www.citrix.com