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From: "Pavel Dovgaluk" <Pavel.Dovgaluk@ispras.ru>
To: 'Peter Maydell' <peter.maydell@linaro.org>
Cc: 'Paolo Bonzini' <pbonzini@redhat.com>,
	'Peter Crosthwaite' <peter.crosthwaite@xilinx.com>,
	'Mark Burton' <mark.burton@greensocs.com>,
	'QEMU Developers' <qemu-devel@nongnu.org>,
	'Frederic Konrad' <fred.konrad@greensocs.com>
Subject: Re: [Qemu-devel] Reverse execution and deterministic replay
Date: Fri, 27 Jun 2014 15:31:55 +0400	[thread overview]
Message-ID: <008601cf91fb$668e89f0$33ab9dd0$@Dovgaluk@ispras.ru> (raw)
In-Reply-To: <CAFEAcA8-5J9ouJREJT=hF1q-dqBd=0JoGz6gG4wBuKbJ7zSOKA@mail.gmail.com>

> On 27 June 2014 11:35, Pavel Dovgaluk <Pavel.Dovgaluk@ispras.ru> wrote:
> > The major disadvantage of icount is that it's updated only on TB boundaries.
> > When one instruction in the middle of the block uses virtual clock, it could
> > have different values for different divisions of the code to TB.
> 
> This is only true if the instruction is incorrectly not
> marked as being "I/O". The idea behind icount is that in
> general we update it on TB boundaries (it's much faster
> than doing it once per insn) but for those places which
> do turn out to need an exact icount we then retranslate
> the block to get the instruction-to-icount-adjustment
> mapping.

I forgot about one more issue.
When qemu stops execution on the breakpoint, the icount
is decreased to the number of instructions in the block.
But in this case the last instruction is not executed and
should not affect the counter.

Pavel Dovgaluk

  parent reply	other threads:[~2014-06-27 11:32 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <53acfed7.e3538c0a.39e2.ffffb619SMTPIN_ADDED_BROKEN@mx.google.com>
2014-06-27  6:11 ` [Qemu-devel] Reverse execution and deterministic replay Peter Crosthwaite
2014-06-27  6:20   ` Pavel Dovgaluk
2014-06-27  7:47   ` Frederic Konrad
2014-06-27 10:35     ` Pavel Dovgaluk
     [not found]     ` <53ad4904.8360e50a.0f7f.ffffce7dSMTPIN_ADDED_BROKEN@mx.google.com>
2014-06-27 10:54       ` Peter Maydell
2014-06-27 11:17         ` Pavel Dovgaluk
2014-06-27 13:43           ` Frederic Konrad
2014-06-27 11:31         ` Pavel Dovgaluk [this message]
     [not found]         ` <53ad5626.82a3700a.2864.fffffc92SMTPIN_ADDED_BROKEN@mx.google.com>
2014-06-27 11:50           ` Peter Maydell
     [not found] <53acfecd.c842e00a.6a5f.45f1SMTPIN_ADDED_BROKEN@mx.google.com>
2014-06-27  8:27 ` Peter Maydell
2014-06-27  5:18 Pavel Dovgaluk

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