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Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet
From: |
Jan Kiszka |
Subject: |
Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups |
Date: |
Mon, 05 Jul 2010 13:13:46 +0200 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 |
Avi Kivity wrote:
> On 07/05/2010 12:07 PM, Jan Kiszka wrote:
>>
>>> What about ack notifiers? Ask the APIC to notify you when an interrupt
>>> is acked. That allows you to track the BSP, all cpus, or some subset.
>>> Masking can be seen at the irq controller level.
>>>
>> So, if I understand you correctly, an IRQ state change that is ignored
>> due to masking would invoke the ack notifier chain as well?
>>
>
> No - the cpu doesn't ack, no ack notifier.
>
> We might need a separate mask notifier. Just add pomodoro sauce.
Mask notifiers would be a must, otherwise you cannot tell apart if an
IRQ was not yet ack'ed or is actually masked. On the other hand... see
below.
>
>>> It's more involved, but provides more information.
>>>
>> Well, it requires to establish ack notifier chains in parallel to the
>> existing IRQ delivery routes. Definitely more invasive.
>>
>
> Right, and need to plumb it twice, once for qemu and once for kvm.
>
> But my feeling is you get a lot more information out of it.
That decoupling between state change and acknowledgment worries me.
Dispatching a source to multiple sinks or sharing a sink between
multiple source is no longer cleanly manageable this way. Just look at
the route of some ISA IRQ on x86: You may get an 'ack' from IOAPIC side
and a 'masked' from the ISA side (or vice versa). And the 'masked' will
arrive earlier. Not really straightforward to handle, is it?
Moreover, it requires a concrete algorithm that takes advantage from the
'ack' information bit (that should be the only additional information
you gain) to justify the additional effort. A "might have some
advantages" is not enough IMO. Do we have such an algorithm already?
Jan
--
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux
- Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups, (continued)
- Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups, Paul Brook, 2010/07/04
- Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups, Jan Kiszka, 2010/07/05
- Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups, Gleb Natapov, 2010/07/05
- Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups, Jan Kiszka, 2010/07/05
- Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups, Gleb Natapov, 2010/07/05
- Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups, Jan Kiszka, 2010/07/05
- Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups, Avi Kivity, 2010/07/05
- Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups, Jan Kiszka, 2010/07/05
- Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups, Gleb Natapov, 2010/07/05
- Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups, Avi Kivity, 2010/07/05
- Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups,
Jan Kiszka <=
- Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups, Avi Kivity, 2010/07/05
- Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups, Jan Kiszka, 2010/07/05
- Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups, Gleb Natapov, 2010/07/05
- Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups, Jan Kiszka, 2010/07/05
- Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups, Avi Kivity, 2010/07/05
- Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups, Gleb Natapov, 2010/07/05
- Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups, Avi Kivity, 2010/07/05
- Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups, Jan Kiszka, 2010/07/05
- Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups, Avi Kivity, 2010/07/05
- Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups, Blue Swirl, 2010/07/05