From: "Pavel Dovgalyuk" <dovgaluk@ispras.ru>
To: 'Paolo Bonzini' <pbonzini@redhat.com>,
'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
Subject: Re: [Qemu-devel] [PATCH v3 3/5] replay: introduce new checkpoint for icount warp
Date: Thu, 10 Mar 2016 12:10:29 +0300 [thread overview]
Message-ID: <000701d17aac$b1645040$142cf0c0$@ru> (raw)
In-Reply-To: <56E0110A.1000205@redhat.com>
> From: Paolo Bonzini [mailto:pbonzini@redhat.com]
> On 01/03/2016 12:07, Pavel Dovgalyuk wrote:
> > qemu_clock_warp function is called to update virtual clock when CPU
> > is sleeping. This function includes replay checkpoint to make execution
> > deterministic in icount mode.
> > Record/replay module flushes async event queue at checkpoints.
> > Some of the events (e.g., block devices operations) include interaction
> > with hardware. E.g., APIC polled by block devices sets one of IRQ flags.
> > Flag to be set depends on currently executed thread (CPU or iothread).
> > Therefore in replay mode we have to process the checkpoints in the same thread
> > as they were recorded.
> > qemu_clock_warp function (and its checkpoint) may be called from different
> > thread. This patch introduces new checkpoint which distinguished warp
> > checkpoint calls from different threads.
> >
> > Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
>
> I think we need two different kinds of "warp" behavior, one to start the
> warp timer (from the main loop and when a timer is set) and one to end it
> (from the CPUs).
>
> Then the need for two checkpoints is much clearer, though I suggestnaming
> them without a reference to TCG; something like CHECKPOINT_CLOCK_WARP_START
> and CHECKPOINT_CLOCK_WARP_ACCOUNT for example.
Thanks, this seems reasonable.
> 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.
Pavel Dovgalyuk
next prev parent reply other threads:[~2016-03-10 9:10 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-01 11:07 [Qemu-devel] [PATCH v3 0/5] Deterministic replay extensions Pavel Dovgalyuk
2016-03-01 11:07 ` [Qemu-devel] [PATCH v3 1/5] replay: character devices Pavel Dovgalyuk
2016-03-01 11:07 ` [Qemu-devel] [PATCH v3 2/5] icount: remove obsolete warp call Pavel Dovgalyuk
2016-03-09 12:05 ` Paolo Bonzini
2016-03-01 11:07 ` [Qemu-devel] [PATCH v3 3/5] replay: introduce new checkpoint for icount warp Pavel Dovgalyuk
2016-03-09 12:03 ` Paolo Bonzini
2016-03-10 9:10 ` Pavel Dovgalyuk [this message]
2016-03-10 10:24 ` Paolo Bonzini
2016-03-01 11:07 ` [Qemu-devel] [PATCH v3 4/5] block: add flush callback Pavel Dovgalyuk
2016-03-09 11:25 ` Kevin Wolf
2016-03-01 11:08 ` [Qemu-devel] [PATCH v3 5/5] replay: introduce block devices record/replay Pavel Dovgalyuk
2016-03-09 11:43 ` Kevin Wolf
2016-03-10 6:15 ` Pavel Dovgalyuk
2016-03-07 7:21 ` [Qemu-devel] [PATCH v3 0/5] Deterministic replay extensions dovgaluk
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='000701d17aac$b1645040$142cf0c0$@ru' \
--to=dovgaluk@ispras.ru \
--cc=Pavel.Dovgaluk@ispras.ru \
--cc=alex.bennee@linaro.org \
--cc=batuzovk@ispras.ru \
--cc=edgar.iglesias@xilinx.com \
--cc=fred.konrad@greensocs.com \
--cc=hines@cert.org \
--cc=igor.rubinov@gmail.com \
--cc=kwolf@redhat.com \
--cc=maria.klimushenkova@ispras.ru \
--cc=mark.burton@greensocs.com \
--cc=pbonzini@redhat.com \
--cc=peter.maydell@linaro.org \
--cc=qemu-devel@nongnu.org \
--cc=real@ispras.ru \
--cc=stefanha@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).