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

From: Alexander Graf
Subject: Re: [Qemu-ppc] [PATCH 6/8] spapr: move interrupt allocator to xics
Date: Mon, 14 Apr 2014 09:34:56 +0200
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:24.0) Gecko/20100101 Thunderbird/24.4.0

On 11.04.14 18:30, Alexey Kardashevskiy wrote:
On 04/12/2014 02:15 AM, Alexander Graf wrote:
On 11.04.14 18:01, Alexey Kardashevskiy wrote:
On 04/12/2014 01:38 AM, Alexander Graf wrote:
On 11.04.14 17:27, Alexey Kardashevskiy wrote:
On 04/12/2014 12:58 AM, Alexander Graf wrote:
On 11.04.14 16:50, Alexey Kardashevskiy wrote:
On 04/11/2014 11:58 PM, Alexander Graf wrote:
On 11.04.2014, at 14:38, Alexey Kardashevskiy <address@hidden> wrote:

On 04/11/2014 07:24 PM, Alexander Graf wrote:
On 10.04.14 16:43, Alexey Kardashevskiy wrote:
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
I put wrong commit message. By change I meant that the default
the destination guest started accepting migration is different
the destination guest became after migration finished. And
avoid changing this default state.
Ok, why is the IRQ configuration different?
Because QEMU creates devices in the order as in the command line,
libvirt changes this order - the XML used to create the guest and
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.
So your patch migrates the current IRQ configuration, but once you
the virtual machine on the destination host it will have different
numbering again, right?
No, why? IRQs are assigned at init time from realize() callbacks (and
survive reset) or as a part of ibm,change-msi rtas call which
happens in
the same order as it only depends on pci addresses and we do not
this either.
Ok, let me rephrase. If I shut the machine down because I'm doing
on-disk hibernate and then boot it back up, will the guest find the
I do not understand what you mean by this. Hibernation by the guest OS
itself or by QEMU? If this involves QEMU exit and QEMU start - then yes,
by the guest OS. The host will only see a genuine "shutdown" event. The
guest OS will expect the machine to look *the exact same* as before the
Ok. So. I have to implement "irq" property everywhere (PHB is missing
INTA/B/C/D now) and check if they did not change during migration via
Hrm. Not sure. Maybe it'd make sense to join next week's call on platform
device creation. The problem seems pretty closely related.
What are those platform devices and what are you going to discuss exactly?
Devices that don't have a unified interrupt routing scheme like PCI where
you just link lines A/B/C/D to your controller and you're good to go.
Ah. VIO in my case.

Why would you need this? I think we already said a couple dozen times that
configuration matching is a bigger problem, no?
For debug! It is not needed in general, yes.

If so (more or less), I still would like to keep patches 1..7.
In fact, the first one is independent and we need it anyway.
IOMMUs do not migrate correctly - they only have a class have and
instance_id and this instance_it depends on command line arguments order.
The #1 patch makes it classname + liobn.
Why do we need a bus for that?

For BusClass::get_dev_path callback to get an unique name.

Juan, I don't think it makes a lot of sense to require a new fake bus just to give us a consistent migration view of things.

Do you have any ideas how to migration busless devices? We could just detect that case and give them numbering based on their occurence in the global QOM hierarchy, no?

Andreas, maybe you have an idea here as well :).


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