Re: [Qemu-devel] [PATCH 6/8] spapr: move interrupt allocator to xics

[Alexey Kardashevskiy]

On 04/10/2014 11:26 PM, Alexander Graf wrote:
> 
> On 10.04.14 15:24, Alexey Kardashevskiy wrote:
>> On 04/10/2014 10:51 PM, Alexander Graf wrote:
>>> On 14.03.14 05:18, Alexey Kardashevskiy wrote:
>>>> The current allocator returns IRQ numbers from a pool and does not
>>>> support IRQs reuse in any form as it did not keep track of what it
>>>> previously returned, it only had the last returned IRQ.
>>>> However migration may change interrupts for devices depending on
>>>> their order in the command line.
>>> Wtf? Nonono, this sounds very bogus and wrong. Migration shouldn't change
>>> anything.
>>
>> I put wrong commit message. By change I meant that the default state before
>> the destination guest started accepting migration is different from what
>> the destination guest became after migration finished. And migration cannot
>> avoid changing this default state.
> 
> Ok, why is the IRQ configuration different?

Because QEMU creates devices in the order as in the command line, and
libvirt changes this order - the XML used to create the guest and the XML
which is sends during migration are different. libvirt thinks it is ok
while it keeps @reg property for (for example) spapr-vscsi devices but it
is not because since the order is different, devices call IRQ allocator in
different order and get different IRQs.



-- 
Alexey