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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Thu, 10 Mar 2016 11:24:21 +0100
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Subject: Re: [Qemu-devel] [PATCH v3 3/5] replay: introduce new checkpoint
	for icount warp
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To: Pavel Dovgalyuk <dovgaluk@ispras.ru>, 'Pavel Dovgalyuk' <Pavel.Dovgaluk@ispras.ru>, qemu-devel@nongnu.org
Cc: edgar.iglesias@xilinx.com, peter.maydell@linaro.org, igor.rubinov@gmail.com, mark.burton@greensocs.com, real@ispras.ru, batuzovk@ispras.ru, maria.klimushenkova@ispras.ru, stefanha@redhat.com, kwolf@redhat.com, hines@cert.org, alex.bennee@linaro.org, fred.konrad@greensocs.com



On 10/03/2016 10:10, Pavel Dovgalyuk wrote:
>> > The start would be where you call qemu_clock_warp(QEMU_CLOCK_VIRTUAL, false):
>> > 
>> >     if (!use_icount) {
>> >         return;
>> >     }
>> >     if (!runstate_is_running()) {
>> >         return;
>> >     }
>> >     if (!replay_checkpoint(CHECKPOINT_CLOCK_WARP_START)) {
>> >         return;
>> >     }
>> >     /* I think calling icount_warp_rt here is unnecessary.  */
>> >     if (!all_cpu_threads_idle()) {
>> >         return;
>> >     }
>> >     if (qtest_enabled()) {
>> >         /* When testing, qtest commands advance icount.  */
>> >         return;
>> >     }
>> > 
>> >     /* We want to use the earliest deadline from ALL vm_clocks */
>> >     clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL_RT);
>> >     deadline = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL);
>> >     ...
>> > 
>> > The end or account function, instead, would be called from tcg_exec_all()
>> > and also from icount_dummy_timer() (this is what makes the call to
>> > icount_warp_rt unnecessary above):
> Why icount_warp_rt is unnecessary? There is no code to proceed the virtual clock.
> Then qemu_start_warp_timer will forever setup the timer without any progress.

If icount_warp_rt is called from icount_dummy_timer(), the virtual clock
will be updated as soon as the VIRTUAL_RT clock reaches the deadline.
It's a much more reasonable place to call icount_warp_rt from (if it
works...).

Paolo