[Qemu-devel] [PATCH v6 00/25] Fixing record/replay and adding reverse debugging

[Artem Pisarenko]

Feature still broken :(

Brief description of my tests.

Guest image is Linux, which just powers off after kernel boots (instead of
proceeding to user-space /init or /sbin/init).
Base cmdline:
qemu-system-x86_64 -nodefaults -machine pc,accel=tcg -m 2048 -cpu qemu64
-rtc clock=vm,base=2000-01-01T00:00:00 -kernel bzImage -initrd rootfs
-append 'nokaslr console=ttyS0 rdinit=/init_poweroff' -nographic -serial
SERIAL_VALUE -icount 1,sleep=off,rr=RR_VALUE,rrfile=icount_rr_capture.bin

Test 1. When SERIAL_VALUE=none
Running with RR_VALUE=record completes successfully.
Running with RR_VALUE=replay doesn't completes. qemu process just eating
~100% cpu and memory usage doesn't grow after some moment. I don't see what
happens because of problem no.2 (see below).

Test 2. When SERIAL_VALUE=stdio
Running with RR_VALUE=record completes successfully.
Running with RR_VALUE=replay caues exit with error:
"qemu-system-x86_64: Missing character write event in the replay log"

These problems are same with qemu 2.12 (both vanilla and with previous
versions of these patches applied). Furthemore, I consider whole icount
mode broken and determinism isn't achievable.
The irony is that I actually don't need record/replay feature. I've tried
to use it only as instrument to debug failing determinism in qemu code. But
since replay/record feature itself relies on determinism, which is broken,
it's no wonder why it fails also (I just hoped to bypass it).

Contact me if you need more details. I just tired a lot trying to get all
these things working... Hope is leaving me...

-- 

С уважением,
  Артем Писаренко