Re: [Qemu-devel] [PATCH 17/21] introduce memory_region_get_address() and use it in kvm/ioapic

[Blue Swirl]

On Fri, Apr 26, 2013 at 10:13 PM, Paolo Bonzini <address@hidden> wrote:
> Il 26/04/2013 19:46, Igor Mammedov ha scritto:
>>> > But as the address can't be changed (yet), the entire patch could be 
>>> > simply:
>>> > -    kioapic->base_address = s->busdev.mmio[0].addr;
>>> > +    kioapic->base_address = IO_APIC_DEFAULT_ADDRESS;
>> It's a bit fragile, but that for sure simpler and can work.
>>
>> Jan, Paolo,
>> Are you ok with this approach?
>>
>
> I think extending memory_region_find is a good idea anyway, and at this
> point I don't see a reason to do the above change...

The reasoning was in the part that Igor cut off:

"Later, when it's possible to change the address via PIIX3 registers,
we can adjust the base and pass that properly to kioapic and on to
KVM.

Resolving the base address every time when kvm_ioapic_put() is called
is also less efficient, assuming of course that the base address
changes less often than the KVM ioctl is used."

I think the patch is a bit flawed. If the guest maps something else on
top of IOAPIC, like LAPIC (which should be in CPU specific address
spaces, but for now it lives in the global system memory space), the
guest could trigger the abort() by resetting the system.

>
> Paolo