Jeremy Fitzhardinge wrote:
> On 09/03/09 05:53, Zhang, Xiantao wrote:
>> I think Jan also answered your question. Dom0 shouldn't touch
>> ioapic after initialization time any more. That is to say, maybe we
>> can find a way to get rid of ioapic from dom0. Actually I can't see
>> why dom0 cares so much about ioapic. Jeremy, do you know the
>> reason ? IMO, dom0 should only cares about GSI and pirq mapping,
>> but currently GSI is always equal to pirq in dom0, so no reason to
>> keep ioapic in dom0.
>>
>
> Yes, I agree. I have a prototype branch:
> git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen.git
> #rebase/dom0/new-interrupt-routing which replaces the whole interrupt
> handing subsystem to avoid any direct interactions with the IO APICs.
Okay, I will read your code and give my comments later.
> I add a new hypercall to directly bind a gsi to a given pirq (which
> has some similarities to your patch). I've attached it below.
> (new-interrupt-routing shouldn't need this patch to function,
> however.)
>
> Unfortunately I haven't had a chance to work on this lately, but when
> I last tried it, it hung shortly after initializing ACPI. I didn't
> get much further than that. I do think, however, that this is this
> right way to go for dom0, esp with regard to upstreaming.
Seems you didn't assign vectors for GSI >= 16 ? Currenlty, hypervisor only
allocate vectors for pin0 -> pin16, so irq_to_vector may not get the vectors
for the required GSI.
> (The second patch is to allow dom0 to get Xen's acpi interrupt model
> so they can always be consistent rather than independently arriving
> at the same result - not not.)
Maybe it is not a must to introduce new hypercall and just using
PHYSDEVOP_map_pirq like MSI side to bind pirq and GSI should work for GSI irqs
also.
For the second patch, maybe we can ignore it since machines produced in recent
10 years should always use the model XEN_ACPI_IRQ_MODEL_IOAPIC. For old
machines, I don't think Xen can run well on them. For the model
XEN_ACPI_IRQ_MODEL_IOSAPIC, it is only available for Intel Itanium processors,
so... :-)
Xiantao
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