Messages in this thread | | | Date | Sun, 20 Sep 2009 22:49:06 +0400 | From | Cyrill Gorcunov <> | Subject | Re: [PATCH] x86: Don't ack_APIC_irq() if lapic is disabled in GENERIC_INTERRUPT_VECTOR handler |
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[Cyrill Gorcunov - Sun, Sep 20, 2009 at 10:42:03PM +0400] | [Cyrill Gorcunov - Sun, Sep 20, 2009 at 10:30:11PM +0400] | ... | | | > | | | > iirc it was Xen related patch. So it's not that simple. | | | > | | | > I've pointed out Sheng about disable_apic. I'm not Xen | | | > specialist but Xen team seem to use specific apic setup | | | > so our "dummy" operations are not involved (case they | | | > set disable_apic=1 without "turn off" apic ops in real). | | | > Something like that. | | | | | | They should then set a NOP function in that case. We really dont want to | | | slow down hotpath functions like smp_generic_interrupt() with flaggery. | | | | | | Ingo | | | | | | | Well, I suppose we should wait for Sheng's comments. | | I wish I would answer you but I simply don't know Xen | | code :) | | | | -- Cyrill | | Wait a bit Ingo, please. It seems I'm having different | patch series in mind. Need to restore mail thread. | Will back soon :) | | -- Cyrill
yeah, it comes from Xen RFC series. Here is a quote from conversation.
> Sheng Yan > > | | is there was some problem with it? I'm asking you > | | because if disable_apic=1 then any apic write/read > | | operations become NOPs. So I don't see how it may > | | hurt. But I could be missing something. > | | > | | -- Cyrill > | > | Ah, I see -- it's due to your other patch... > | Hmm this makes all "disable apic" idea less > | general. And safety of ack_APIC_irq is now > | under suspicious. > > Um, probably. I've seen a ack_APIC_irq() in do_IRQ when handle_irq() fail. > Seems the assumption that ack_APIC_irq() always safe is there. I will check if > I can make it more elegant - maybe disable the warning in the Xen code... >
Personally, I think "out-of-xen-thread" this patch is not needed. And if this apic-ack operation causes any kind of problems -- this problem should be fixed without disable_apic involved.
-- Cyrill
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