From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49130) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1adwcB-0001Xs-Q5 for qemu-devel@nongnu.org; Thu, 10 Mar 2016 04:10:45 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1adwc7-0003QT-JC for qemu-devel@nongnu.org; Thu, 10 Mar 2016 04:10:39 -0500 Received: from mail.ispras.ru ([83.149.199.45]:46620) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1adwc7-0003QL-7Q for qemu-devel@nongnu.org; Thu, 10 Mar 2016 04:10:35 -0500 From: "Pavel Dovgalyuk" References: <20160301110732.10104.2019.stgit@PASHA-ISP> <20160301110752.10104.65295.stgit@PASHA-ISP> <56E0110A.1000205@redhat.com> In-Reply-To: <56E0110A.1000205@redhat.com> Date: Thu, 10 Mar 2016 12:10:29 +0300 Message-ID: <000701d17aac$b1645040$142cf0c0$@ru> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Content-Language: ru Subject: Re: [Qemu-devel] [PATCH v3 3/5] replay: introduce new checkpoint for icount warp List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: 'Paolo Bonzini' , 'Pavel Dovgalyuk' , 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 > 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 > > 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