From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39588) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1X1y55-0006Gu-Fh for qemu-devel@nongnu.org; Tue, 01 Jul 2014 09:26:49 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1X1y50-0004hY-0d for qemu-devel@nongnu.org; Tue, 01 Jul 2014 09:26:43 -0400 Received: from [2001:41d0:8:2b42::1] (port=50142 helo=greensocs.com) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1X1y4z-0004hN-NB for qemu-devel@nongnu.org; Tue, 01 Jul 2014 09:26:37 -0400 Message-ID: <53B2B70C.8060908@greensocs.com> Date: Tue, 01 Jul 2014 15:26:36 +0200 From: Frederic Konrad MIME-Version: 1.0 References: <007401cf951e$0c5bbd10$25133730$@Dovgaluk@ispras.ru> <53B2AC46.8050402@greensocs.com> <53B2B379.8010100@ispras.ru> In-Reply-To: <53B2B379.8010100@ispras.ru> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC PATCH 00/22] Reverse execution and deterministic replay List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Vasily Eefimov , Pavel Dovgaluk , 'QEMU Developers' Cc: 'Paolo Bonzini' , 'Peter Crosthwaite' , 'Mark Burton' , 'Peter Maydell' On 01/07/2014 15:11, Vasily Eefimov wrote: > > > On 01.07.2014 16:40, Frederic Konrad wrote: >> Hi Pavel, >> >> Thanks for sharing. >> I'll take a look at your patch-set. >> I suggest you try the icount mechanism and I think it might be > There is a problem with icount. I know it operates in two ways: > counting VCPU instructions (with TB size accuracy) and "warp"ing with > respect to host clock. The last one is necessary for interrupts, > timers (and other asynchronous events) while VCPU is halted (and other > cases in which VCPU instructions is not being executed). So, this > referencing to host clock (which is non-deterministic) make icount a > source of non-determinism. Hence, it cannot be used as deterministic > timer (for synchronization of asynchronous non-deterministic events) > while playing. True, this is right for virtual clock. That's why we built a new clock which didn't take this warping in account but becomes deterministically correct relative to the instruction counter. Fred >> interesting to >> combine our work to have a complete solution and to avoid double copy >> patches >> (for example command lines, gdb stub and the snapshot mechanism). >> >> I'll provides the last updates today or tomorrow. >> >> Also do you have any git tree somewhere so it is easier for us to >> test it? >> I recommand you to use git send-email to submit your patches so you >> can CC >> people and the patch set won't be cutted by other patches in the mailing >> list. >> >> Thanks, >> Fred >> >> On 01/07/2014 13:17, Pavel Dovgaluk wrote: >>> Hi, >>> >>> This set of patches is related to the reverse execution and >>> deterministic >>> replay of qemu execution Our implementation of replay can be used for >>> deterministic and reverse debugging of guest code through gdb >>> remote interface. >>> >>> Execution recording writes non-deterministic events log, which can be >>> later >>> used for replaying the execution anywhere and for unlimited number of >>> times. >>> It also supports checkpointing for faster rewinding during reverse >>> debugging. >>> Execution replaying reads the log and replays all non-deterministic >>> events >>> including external input, hardware clocks, and interrupts. >>> >>> Reverse execution has the following features: >>> * Deterministically replays whole system execution and all contents >>> of the memory, >>> state of the hadrware devices, clocks, and screen of the VM. >>> * Writes execution log into the file for latter replaying for >>> multiple times >>> on different machines. >>> * Supports i386, x86_64, and ARM hardware platforms. >>> * Performs deterministic replay of all operations with keyboard, >>> mouse, network adapters, >>> audio devices, serial interfaces, and physical USB devices >>> connected to the emulator. >>> * Provides support for gdb reverse debugging commands like >>> reverse-step and reverse-continue. >>> * Supports auto-checkpointing for convenient reverse debugging. >>> * Allows "going to the live execution" from the replay mode. >>> >>> Usage of the record/replay: >>> * First, record the execution, by adding '-record fname=replay.bin' >>> to the >>> command line. >>> * Then you can replay it for the multiple times by using another >>> command >>> line option: '-replay fname=replay.bin' >>> * Virtual machine should have at least one virtual disk, which is >>> used to >>> store checkpoints. If you want to enable automatic checkpointing, >>> simply >>> add ',period=XX' to record options, where XX is the checkpointing >>> period >>> in seconds. >>> * Using of the network adapters in record/replay mode is possible >>> with >>> the following command-line options: >>> - '-net user' (or another host adapter) in record mode >>> - '-net replay' in replay mode. Every host network adapter >>> should be >>> replaced by 'replay' when replaying the execution. >>> * Reverse debugging can be used through gdb remote interface. >>> reverse-stepi and reverse-continue commands are supported. Other >>> reverse >>> commands should also work, because they reuse these ones. >>> * Monitor is extended by the following commands: >>> - replay_info - prints information about replay mode and current >>> step >>> (number of instructions executed) >>> - replay_break - sets "breakpoint" at the specified instructions >>> count. >>> - replay_seek - rewinds (using the checkpoints, if possible) to the >>> specified step of replay log. >>> - replay_events - prints list of the external events like network >>> packet >>> input, or keyboard and mouse input. >>> >>> Paper with short description of deterministic replay implementation: >>> http://www.computer.org/csdl/proceedings/csmr/2012/4666/00/4666a553-abs.html >>> >>> > ... >>> Pavel Dovgalyuk >>> >> >> >