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Re: [Qemu-devel] [PATCH 11/22] i8259: Update IRQ state after reset


From: Avi Kivity
Subject: Re: [Qemu-devel] [PATCH 11/22] i8259: Update IRQ state after reset
Date: Sun, 02 Oct 2011 16:17:37 -0400 (EDT)

> >
> > It doesn't help.  There is propagation delay there as well.  If the
> > input wins the race against reset, the launch sequence is started.
>
> To bring the example back to QEMU, a disk write could be issued or
> network packet could be sent. But still, this only confirms that
> during the initial phase of reset, no output activities can be
> allowed
> to avoid such problems.

In fact these aren't problems.  The packet may be sent or data written, as long 
as they aren't corrupted.  A device is allowed to "delay" a reset (but not 
indefinitely).


> > Okay.  I still don't think there is a problem.
>
> There is, Jan's real example and my theoretical cases show that.
>

I believe your example has the same problem on real hardware.  Jan, is your 
problem not solved by two-phase reset?



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