From patchwork Thu May 26 08:45:29 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pavel Dovgalyuk X-Patchwork-Id: 12862104 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id A1D3DC433F5 for ; Thu, 26 May 2022 08:57:06 +0000 (UTC) Received: from localhost ([::1]:56340 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nu9In-0005JF-6M for qemu-devel@archiver.kernel.org; Thu, 26 May 2022 04:57:05 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:50440) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nu97f-0004uj-4v for qemu-devel@nongnu.org; Thu, 26 May 2022 04:45:37 -0400 Received: from mail.ispras.ru ([83.149.199.84]:49756) by eggs.gnu.org with esmtps (TLS1.2:DHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nu97d-0004VL-9O for qemu-devel@nongnu.org; Thu, 26 May 2022 04:45:34 -0400 Received: from [127.0.1.1] (unknown [85.142.117.226]) by mail.ispras.ru (Postfix) with ESMTPSA id 6319440755F0; Thu, 26 May 2022 08:45:29 +0000 (UTC) Subject: [PATCH v3 5/9] docs: convert docs/devel/replay page to rst From: Pavel Dovgalyuk To: qemu-devel@nongnu.org Cc: pavel.dovgalyuk@ispras.ru, pbonzini@redhat.com, alex.bennee@linaro.org, crosa@redhat.com, f4bug@amsat.org Date: Thu, 26 May 2022 11:45:29 +0300 Message-ID: <165355472918.533615.4953699104859977763.stgit@pasha-ThinkPad-X280> In-Reply-To: <165355470196.533615.1219754093587154582.stgit@pasha-ThinkPad-X280> References: <165355470196.533615.1219754093587154582.stgit@pasha-ThinkPad-X280> User-Agent: StGit/0.23 MIME-Version: 1.0 Received-SPF: pass client-ip=83.149.199.84; envelope-from=pavel.dovgalyuk@ispras.ru; helo=mail.ispras.ru X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" This patch converts prior .txt replay devel documentation to .rst. Signed-off-by: Pavel Dovgalyuk Reviewed-by: Richard Henderson --- docs/devel/index-tcg.rst | 1 + docs/devel/replay.rst | 54 ++++++++++++++++++++++++++++++++++++++++++++++ docs/devel/replay.txt | 46 --------------------------------------- 3 files changed, 55 insertions(+), 46 deletions(-) create mode 100644 docs/devel/replay.rst delete mode 100644 docs/devel/replay.txt diff --git a/docs/devel/index-tcg.rst b/docs/devel/index-tcg.rst index 0b0ad12c22..7b9760b26f 100644 --- a/docs/devel/index-tcg.rst +++ b/docs/devel/index-tcg.rst @@ -13,3 +13,4 @@ are only implementing things for HW accelerated hypervisors. multi-thread-tcg tcg-icount tcg-plugins + replay diff --git a/docs/devel/replay.rst b/docs/devel/replay.rst new file mode 100644 index 0000000000..dd8bf3b195 --- /dev/null +++ b/docs/devel/replay.rst @@ -0,0 +1,54 @@ +.. + Copyright (c) 2022, ISP RAS + Written by Pavel Dovgalyuk + +======================= +Execution Record/Replay +======================= + +Record/replay mechanism, that could be enabled through icount mode, expects +the virtual devices to satisfy the following requirements. + +The main idea behind this document is that everything that affects +the guest state during execution in icount mode should be deterministic. + +Timers +------ + +All virtual devices should use virtual clock for timers that change the guest +state. Virtual clock is deterministic, therefore such timers are deterministic +too. + +Virtual devices can also use realtime clock for the events that do not change +the guest state directly. When the clock ticking should depend on VM execution +speed, use virtual clock with EXTERNAL attribute. It is not deterministic, +but its speed depends on the guest execution. This clock is used by +the virtual devices (e.g., slirp routing device) that lie outside the +replayed guest. + +Bottom halves +------------- + +Bottom half callbacks, that affect the guest state, should be invoked through +replay_bh_schedule_event or replay_bh_schedule_oneshot_event functions. +Their invocations are saved in record mode and synchronized with the existing +log in replay mode. + +Saving/restoring the VM state +----------------------------- + +All fields in the device state structure (including virtual timers) +should be restored by loadvm to the same values they had before savevm. + +Avoid accessing other devices' state, because the order of saving/restoring +is not defined. It means that you should not call functions like +'update_irq' in post_load callback. Save everything explicitly to avoid +the dependencies that may make restoring the VM state non-deterministic. + +Stopping the VM +--------------- + +Stopping the guest should not interfere with its state (with the exception +of the network connections, that could be broken by the remote timeouts). +VM can be stopped at any moment of replay by the user. Restarting the VM +after that stop should not break the replay by the unneeded guest state change. diff --git a/docs/devel/replay.txt b/docs/devel/replay.txt deleted file mode 100644 index e641c35add..0000000000 --- a/docs/devel/replay.txt +++ /dev/null @@ -1,46 +0,0 @@ -Record/replay mechanism, that could be enabled through icount mode, expects -the virtual devices to satisfy the following requirements. - -The main idea behind this document is that everything that affects -the guest state during execution in icount mode should be deterministic. - -Timers -====== - -All virtual devices should use virtual clock for timers that change the guest -state. Virtual clock is deterministic, therefore such timers are deterministic -too. - -Virtual devices can also use realtime clock for the events that do not change -the guest state directly. When the clock ticking should depend on VM execution -speed, use virtual clock with EXTERNAL attribute. It is not deterministic, -but its speed depends on the guest execution. This clock is used by -the virtual devices (e.g., slirp routing device) that lie outside the -replayed guest. - -Bottom halves -============= - -Bottom half callbacks, that affect the guest state, should be invoked through -replay_bh_schedule_event or replay_bh_schedule_oneshot_event functions. -Their invocations are saved in record mode and synchronized with the existing -log in replay mode. - -Saving/restoring the VM state -============================= - -All fields in the device state structure (including virtual timers) -should be restored by loadvm to the same values they had before savevm. - -Avoid accessing other devices' state, because the order of saving/restoring -is not defined. It means that you should not call functions like -'update_irq' in post_load callback. Save everything explicitly to avoid -the dependencies that may make restoring the VM state non-deterministic. - -Stopping the VM -=============== - -Stopping the guest should not interfere with its state (with the exception -of the network connections, that could be broken by the remote timeouts). -VM can be stopped at any moment of replay by the user. Restarting the VM -after that stop should not break the replay by the unneeded guest state change.