From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37195) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fQ6uW-0000Ip-JD for qemu-devel@nongnu.org; Tue, 05 Jun 2018 04:01:45 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fQ6uS-00083C-1z for qemu-devel@nongnu.org; Tue, 05 Jun 2018 04:01:44 -0400 Received: from mail-wr0-x244.google.com ([2a00:1450:400c:c0c::244]:40846) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1fQ6uR-00082S-PU for qemu-devel@nongnu.org; Tue, 05 Jun 2018 04:01:39 -0400 Received: by mail-wr0-x244.google.com with SMTP id l41-v6so1291425wre.7 for ; Tue, 05 Jun 2018 01:01:39 -0700 (PDT) References: <20180528071332.9424.27343.stgit@pasha-VirtualBox> <87in6yd146.fsf@linaro.org> <001201d3fc8d$e8a06390$b9e12ab0$@ru> From: Alex =?utf-8?Q?Benn=C3=A9e?= In-reply-to: <001201d3fc8d$e8a06390$b9e12ab0$@ru> Date: Tue, 05 Jun 2018 09:01:37 +0100 Message-ID: <87h8mhd5lq.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v4 00/19] reverse debugging List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Pavel Dovgalyuk Cc: 'Pavel Dovgalyuk' , qemu-devel@nongnu.org, kwolf@redhat.com, peter.maydell@linaro.org, war2jordan@live.com, crosthwaite.peter@gmail.com, boost.lists@gmail.com, quintela@redhat.com, ciro.santilli@gmail.com, jasowang@redhat.com, mst@redhat.com, zuban32s@gmail.com, armbru@redhat.com, maria.klimushenkova@ispras.ru, kraxel@redhat.com, thomas.dullien@googlemail.com, pbonzini@redhat.com, mreitz@redhat.com, dgilbert@redhat.com, rth@twiddle.net Pavel Dovgalyuk writes: >> From: Alex Benn=C3=A9e [mailto:alex.bennee@linaro.org] >> Pavel Dovgalyuk writes: >> >> > Ping? >> >> I started having a look but I ran into this straight away. First I >> recorded a boot of the kernel: >> >> ./aarch64-softmmu/qemu-system-aarch64 -machine virt,graphics=3Don,gic- >> version=3D3,virtualization=3Don -cpu cortex-a53 --serial mon:stdio -disp= lay none -kernel >> ../images/aarch64-current-linux-initrd-guest.img -icount shift=3D7,rr=3D= record,rrfile=3Dreplay.bin >> >> Then played back: >> >> ./aarch64-softmmu/qemu-system-aarch64 -machine virt,graphics=3Don,gic- >> version=3D3,virtualization=3Don -cpu cortex-a53 --serial mon:stdio -disp= lay none -kernel >> ../images/aarch64-current-linux-initrd-guest.img -icount shift=3D7,rr=3D= replay,rrfile=3Dreplay.bin - >> s -S > > This looks ok, but... > >> And did the following on gdb: >> >> (gdb) i >> 0x0000000040000004 in ?? () >> =3D> 0x40000004: mov x1, xzr >> 0x40000008: mov x2, xzr >> 0x4000000c: mov x3, xzr >> (gdb) >> 0x0000000040000008 in ?? () >> =3D> 0x40000008: mov x2, xzr >> 0x4000000c: mov x3, xzr >> 0x40000010: ldr x4, 0x40000020 >> (gdb) >> 0x000000004000000c in ?? () >> =3D> 0x4000000c: mov x3, xzr >> 0x40000010: ldr x4, 0x40000020 >> 0x40000014: br x4 >> (gdb) >> 0x0000000040000010 in ?? () >> =3D> 0x40000010: ldr x4, 0x40000020 >> 0x40000014: br x4 >> 0x40000018: .inst 0x44000000 ; undefined >> (gdb) >> 0x0000000040000014 in ?? () >> =3D> 0x40000014: br x4 >> 0x40000018: .inst 0x44000000 ; undefined >> 0x4000001c: .inst 0x00000000 ; undefined >> (gdb) p/x $x4 >> $1 =3D 0x40080000 >> (gdb) reverse-stepi >> warning: Remote failure reply: E14 >> >> Surely this is the simple case and doesn't require any snapshots for >> block devices as there are none. Am I missing something? > > Reverse debugging requires the snapshotting. QEMU can't revert the VM sta= te without the snapshots. > You can try adding an empty qcow2 image to allow snapshotting there. I got confused with block device snapshots and rr snapshots. Let me try again ;-) -- Alex Benn=C3=A9e