linux-kernel - Re: [kvm-devel] [RFC] Deferred interrupt handling.

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Message-ID: <20070725141813.GE9256@ucw.cz>
Date:	Wed, 25 Jul 2007 14:18:14 +0000
From:	Pavel Machek <pavel@....cz>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Dor Laor <dor.laor@...ranet.com>, Avi Kivity <avik@...ranet.com>,
	kvm-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	Greg KH <greg@...ah.com>
Subject: Re: [kvm-devel] [RFC] Deferred interrupt handling.

Hi!

I guess this will also allow UIO to work without _any_ kernel parts,
with only slight performance penalty in 'almost-never-happens'
deadlock case?

(Greg, details are below, and better description is in the lkml
thread).
							Pavel

> > - Our dummy handler will always return IRQ_HANDLED in case any other
> > previous
> >   irqaction did not return such. It will also issue the timer and mask
> > the irq in this case.
> 
> Ok
> 
> >   btw, if I'm not mistaken only after bad 99900/100000 the irq is
> > disabled.
> 
> (and with GIT providing that they occurred in a short time period)
> 
> > - If the timer pops before the guest acks the irq, the timer handler
> > will
> >   ack the irq and unmask it. The timer's job is only to prevent
> > deadlocks.
> 
> Ok I see what you are doing. It's either inspired or insane and I am not
> quite sure which of the two. I agree it should work although may cause
> performance crunches now and then and will also need care getting the
> locking right.

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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