On 8/27/2013 1:41 AM, Jan Beulich wrote:
>>>> On 27.08.13 at 03:21, Suravee Suthikulpanit <suravee.suthikulpanit@amd.com> wrote:
>> I have been trying to test out this patch.  Somehow, I could not get Xen
>> boot option to exercise the code path.  What boot configuration are you
>> using to test this?
> I don't have a system suitable for testing this; Sander did. The main
> requirement apart from having an IOMMU is to also have a HPET
> with at least on MSI-capable channel. Otherwise code won't get
> here. The normal flow is
>
> hpet_broadcast_init() -> hpet_fsb_cap_lookup() -> hpet_assign_irq()
> -> hpet_setup_msi_irq() -> iommu_setup_hpet_msi()
>
> Jan
Ah,ok.. I found out thatthisonly applies on the family10h system with 
IOMMUdue to the check in arch/x86/time.c:_disable_pit_irq

"if (!boot_cpu_has(X86_FEATURE_ARAT))"

and the condition in arch/x86/cpu/amd.c:_init_amd()

     /*
      * Family 0x12 and above processors have APIC timer
      * running in deep C states.
      */
     if (c->x86 > 0x11)
         set_bit(X86_FEATURE_ARAT, c->x86_capability);

Jan, doyou think you could also add the comment that this only 
applicable on family10h?

Acked-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>

Thank you,

Suravee.