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Re: [Qemu-ppc] [PATCH 17/25] spapr: add a sPAPRXive object to the machin
Cédric Le Goater
Re: [Qemu-ppc] [PATCH 17/25] spapr: add a sPAPRXive object to the machine
Mon, 4 Dec 2017 09:32:00 +0100
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On 12/04/2017 02:59 AM, David Gibson wrote:
> On Fri, Dec 01, 2017 at 09:10:24AM +0100, Cédric Le Goater wrote:
>> On 12/01/2017 05:14 AM, David Gibson wrote:
>>> On Thu, Nov 30, 2017 at 03:15:09PM +0000, Cédric Le Goater wrote:
>>>> On 11/30/2017 05:55 AM, David Gibson wrote:
>>>>> On Thu, Nov 23, 2017 at 02:29:47PM +0100, Cédric Le Goater wrote:
>>>>>> The XIVE object is designed to be always available, so it is created
>>>>>> unconditionally on newer machines.
>>>>> There doesn't actually seem to be anything dependent on machine
>>>>> version here.
>>>> No. I thought that was too early in the patchset. This is handled
>>>> in the last patch with a 'xive_exploitation' bool which is set to
>>>> false on older machines.
>>>> But, nevertheless, the XIVE objects are always created even if not
>>>> used. Something to discuss.
>>> That'll definitely break backwards migration, since the destination
>>> won't understand the (unused but still present) xive state it
>> no because it's not sent. the vmstate 'needed' op of the sPAPRXive
>> object discards it :
>> static bool vmstate_spapr_xive_needed(void *opaque)
>> sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
>> return spapr->xive_exploitation;
> Ah, sorry, missed that. Once we have negotiation we'll need to make
> sure the xive_exploitation bit is sent first, of course, but I'm
> pretty sure the machine state is already sent first.
>>> So xives can only be created on new machine types.
>> That would be better I agree. I can probably use the 'xive_exploitation'
>> bool to condition its creation.
> Hrm. I'm less sure about that - I'm not sure the lifetimes line up.
> But I'd like to avoid creating them on earlier machine types, even if
> xive_exploitation can't do the trick.
Yes. I agree. I think we can work something out without introducing
too much complexity. The XIVE object is directly used by the
machine only to set/unset IRQ numbers. Otherwise, it is always
conditioned by :
I think adding a couple of more tests on the 'xive_exploitation'
bool should work out for older machines.