From: Alexey Kardashevskiy <aik@ozlabs.ru>
To: Alexander Graf <agraf@suse.de>, qemu-devel@nongnu.org
Cc: qemu-ppc@nongnu.org, "Andreas Färber" <afaerber@suse.de>
Subject: Re: [Qemu-devel] [PATCH 6/8] spapr: move interrupt allocator to xics
Date: Fri, 11 Apr 2014 22:38:59 +1000 [thread overview]
Message-ID: <5347E263.7050605@ozlabs.ru> (raw)
In-Reply-To: <5347B4D3.9060508@suse.de>
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 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.
>
> So your patch migrates the current IRQ configuration, but once you restart
> the virtual machine on the destination host it will have different IRQ
> 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 change
this either.
> I'm not sure that's a good solution to the problem. I guess we should
> rather aim to make sure that we can make IRQ allocation explicit.
> Fundamentally the problem sounds very similar to the PCI slot allocation
> which eventually got solved by libvirt specifying the slots manually.
We can do that too. Who decides? :)
--
Alexey
next prev parent reply other threads:[~2014-04-11 12:39 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-14 4:18 [Qemu-devel] [PATCH 0/8] spapr: fix IOMMU and XICS/IRQs migration Alexey Kardashevskiy
2014-03-14 4:18 ` [Qemu-devel] [PATCH 1/8] spapr-iommu: add a bus for spapr-iommu devices Alexey Kardashevskiy
2014-04-10 12:40 ` Alexander Graf
2014-04-10 14:40 ` Alexey Kardashevskiy
2014-04-10 14:52 ` Andreas Färber
2014-04-10 15:18 ` Alexey Kardashevskiy
2014-03-14 4:18 ` [Qemu-devel] [PATCH 2/8] xics: add flags for interrupts Alexey Kardashevskiy
2014-04-10 12:43 ` Alexander Graf
2014-03-14 4:18 ` [Qemu-devel] [PATCH 3/8] xics: add find_server Alexey Kardashevskiy
2014-03-14 4:18 ` [Qemu-devel] [PATCH 4/8] xics: add pre_load() hook to ICSStateClass Alexey Kardashevskiy
2014-03-14 4:18 ` [Qemu-devel] [PATCH 5/8] xics: disable flags reset on xics reset Alexey Kardashevskiy
2014-03-14 4:18 ` [Qemu-devel] [PATCH 6/8] spapr: move interrupt allocator to xics Alexey Kardashevskiy
2014-04-10 12:51 ` Alexander Graf
2014-04-10 13:24 ` Alexey Kardashevskiy
2014-04-10 13:26 ` Alexander Graf
2014-04-10 14:43 ` Alexey Kardashevskiy
2014-04-11 9:24 ` Alexander Graf
2014-04-11 12:38 ` Alexey Kardashevskiy [this message]
2014-04-11 13:58 ` Alexander Graf
2014-04-11 14:50 ` Alexey Kardashevskiy
2014-04-11 14:58 ` Alexander Graf
2014-04-11 15:27 ` Alexey Kardashevskiy
2014-04-11 15:38 ` Alexander Graf
2014-04-11 16:01 ` Alexey Kardashevskiy
2014-04-11 16:15 ` Alexander Graf
2014-04-11 16:30 ` Alexey Kardashevskiy
2014-03-14 4:18 ` [Qemu-devel] [PATCH 7/8] spapr: remove @next_irq Alexey Kardashevskiy
2014-03-14 7:19 ` Thomas Huth
2014-03-14 4:18 ` [Qemu-devel] [PATCH 8/8] xics: enable interrupt configuration reset on migration Alexey Kardashevskiy
2014-04-10 12:55 ` Alexander Graf
2014-03-20 1:25 ` [Qemu-devel] [PATCH 0/8] spapr: fix IOMMU and XICS/IRQs migration Andreas Färber
2014-04-04 5:53 ` Alexey Kardashevskiy
2014-05-04 13:56 ` Alexey Kardashevskiy
2014-05-04 21:52 ` Paolo Bonzini
2014-05-04 23:48 ` Alexey Kardashevskiy
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