Re: [Xen-devel] [PATCH] x86/hvm: implement save/restore for posted interrupts

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 25.07.14 at 14:49, <kevin.tian@xxxxxxxxx> wrote:
>>  From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
>> Sent: Friday, July 25, 2014 2:41 AM
>> 
>> >>> On 03.07.14 at 17:09, <olaf@xxxxxxxxx> wrote:
>> > Saving and restoring a PVonHVM guest on a host which has the VMX
>> > "Posted Interrupt Processing" feature enabled will fail because the
>> > xen-platform-pci device does not receive interrupts anymore after
>> > restore. The reason is that the IRQs are not maintained in APIC_IRR,
>> > but in a separate PIR array. This info is lost during the save
>> > operation.
>> >
>> > Syncing the PIR state into IRR during save, and restoring the state
>> > later will fix 'xm save/restore' of a PVonHVM guest.
>> >
>> > Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
>> 
>> Guys, where are we with this? Afaict all simplification suggestions
>> you provided so far yielded a non-working patch. Are you actively
>> working on getting a working alternative, or can we get an ack on
>> what Olaf submitted?
>> 
> 
> I hope Olaf can figure out why sync_irr_to_pir is actually required before
> I can ack.

I was thinking it would be the other way around: You suggesting it's
not needed (which is wrong according to observations) would offer
an explanation and/or a working alternative fix. I don't think you can
expect Olaf to explain why what you suggest doesn't work, even
more so with _you_ being the VMX maintainer.

Jan


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