Re: [Qemu-devel] [0.14?][PATCH 3/4] ioapic: Prepare for base address relocation

[Blue Swirl]

On Thu, Feb 3, 2011 at 5:43 PM, Jan Kiszka <address@hidden> wrote:
> On 2011-02-03 18:36, Blue Swirl wrote:
>> On Thu, Feb 3, 2011 at 5:18 PM, Jan Kiszka <address@hidden> wrote:
>>> On 2011-02-03 18:03, Blue Swirl wrote:
>>>> On Thu, Feb 3, 2011 at 2:55 PM, Jan Kiszka <address@hidden> wrote:
>>>>> The registers of real IOAPICs can be relocated during runtime (via
>>>>> chipset registers). We don't support this yet, but qemu-kvm carries the
>>>>> current base address in its version 2 vmstate.
>>>>>
>>>>> To align both implementations for migratability, add the proper
>>>>> infrastructure to accept initial as well as updated base addresses and
>>>>> include the current address in the vmstate. This is done in a way that
>>>>> will also allow multiple IOAPICs in the future.
>>>>
>>>> Nack, the addresses should be device properties.
>>>
>>> Hmm.... we could make default_base_address a property. Will change that.
>>> But current_base_address is just the same as apicbase and can't be a
>>> property.
>>
>> Oh, right. What will current_base_address used for? Why can't board
>> just unmap IOAPIC from current address and remap it at the new
>> address? Then the device would not need to know its base address.
>
> The board could do this. The question is where we put this service, in
> the context if the IOAPIC as ioapic_set_base_address (compare to
> cpu_set_apic_base - which is buggy as it lacks sysbus_mmio_map) or into
> each and every board code. In the latter case, the boards would also be
> responsible for saving/restoring the address.

How is the device relocated? Where are the chipset registers you mention?