* Linus Torvalds <torva...@linux-foundation.org> wrote:
> On Fri, Feb 20, 2015 at 11:41 AM, Ingo Molnar <mi...@kernel.org> wrote:
> >
> > I'm not so sure about that aspect: I think disabling
> > IRQs might be necessary with some APICs (if lower
> > levels don't disable IRQs), to make sure the 'local
> > APIC busy' bit isn't set:
>
> Right. But afaik not for the x2apic case, which this is.
> The x2apic doesn't even have a busy bit, and sending the
> ipi is a single write,
Ah, ok! Then the patch looks good to me.
( Originally we didn't wait for the ICR bit either, but
then it was added due to later erratas and was eventually
made an architectural requirement. )
> I agree that when doing other apic implementations, we
> may need to guarantee atomicity for things like "wait for
> apic idle, then send the ipi".
Yeah.
Thanks,
Ingo
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