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From: "Pavel Dovgaluk" <Pavel.Dovgaluk@ispras.ru>
References: <002101cba1ca$2cae3070$860a9150$@Dovgaluk@ispras.ru>
	<201012221235.14145.paul@codesourcery.com>
In-Reply-To: <201012221235.14145.paul@codesourcery.com>
Subject: RE: [Qemu-devel] Deterministic replay
Date: Wed, 22 Dec 2010 15:43:12 +0300
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To: 'Paul Brook' <paul@codesourcery.com>, qemu-devel@nongnu.org

> >  I am working on implementation of deteministic execution replay
> technology
> > for Qemu. It should be similar to VMWare's replay debugging.
> >
> >  To make alarm timer (which invokes host_alarm_handler function)
> > determinisic, I changed it's behavior: it sets flag, that execution
> should
> > be stopped and this flag is checked before every instruction in the
> > translated code.
> 
> You don't need to do this. A much better solution is to not use the
> host timer
> at all. See -icount.

 Thank you for your reply. 
 I know, that there is a virtual timers, that are enabled by -icount option
and can be used to get rid of host timers usage.
 But the problem is different - I need to synchronize alarm thread, which
breaks the execution of guest code to allow processing interrupts and
interaction with VNC/GDB/...
 Events caused by alarm thread are non-deterministic and asynchronous. To
save these events in the execution log (for latter replay) I need to
synchronize them with execution of guest code.
 The way which I am using for it is allowing execution stop at any point of
the guest code.


Pavel Dovgaluk