On 2015/1/13 18:09, David Vrabel wrote:
> On 13/01/15 02:23, Jiang Liu wrote:
>> On 2015/1/12 23:01, David Vrabel wrote:
>>> On 12/01/15 13:39, Jiang Liu wrote:
>>>> Commit b81975eade8c ("x86, irq: Clean up irqdomain transition code")
>>>> breaks xen IRQ allocation because xen_smp_prepare_cpus() doesn't invoke
>>>> setup_IO_APIC(), so no irqdomains created for IOAPICs and
>>>> mp_map_pin_to_irq() fails at the very beginning.
>>>>
>>>> Enhance xen_smp_prepare_cpus() to call setup_IO_APIC() to initialize
>>>> irqdomain for IOAPICs.
>>>
>>> Having Xen call setup_IO_APIC() to initialize the irq domains then having to
>>> add special cases to it is just wrong.
>>>
>>> The bits of init deferred by mp_register_apic() are also deferred to
>>> two different places which looks odd.
>>>
>>> What about something like the following (untested) patch?
>> Hi David,
>> Really appreciate your suggestions about Xen IOAPIC:)
>> Your patch solves the issue, but it will break a coming patch
>> set to enable hierarchy irqdomain on x86.
>
> For 3.19 I would recommend this patch. Since it's been tested and it's
> pretty small. Can you spin a version of this with a proper changelog.
> please?
Hi David,
Good suggestion, I will send out the patch tomorrow.
Regards!
Gerry
>
>> To enable hierarchy irqdomain on x86, need to build
>> irqdomains in following order:
>> 1) create irqdomain for CPU vector domain
>> 2) create irqdomains for interrupt remapping unit if interrupt
>> remapping is enabled.
>> 3) create irqdomains for IOAPIC/MSI/HPET etc.
>>
>> Function arch_early_ioapic_init() is called before initializing
>> interrupt remapping subsystem. So creating IOAPIC irqdomains in
>> arch_early_ioapic_init() will break hierarchy irqdomain with
>> interrupt remapping enabled. I will post the x86 hierarchy
>> irqdomain patch soon.
>>
>> So could you please help to advice on:
>
> I don't know enough about this area to comment on these authoritatively
> and I don't have time to look into this in more detail right now, but to
> the best of my understanding.
>
>> 1) Is IOAPIC irqdomain needed for PV?
>
> PV dom0 only requires a mechanism to obtain properties of the IOAPIC
> interrupt lines. The actual physical interrupts are delivered to the
> hypervisor. It doesn't require any of the irq setup.
>
>> 2) Is IOAPIC irqdomain needed for HVM?
>
> Yes.
>
>> 3) Is IOAPIC irqdomain needed for Dom0?
>
>
> See (1) above.
>
>> 4) What's the proper hook point to create IOAPIC irqdomain for Xen
>> UP systems?
>
> Don't know.
>
> David
>
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