From: KONRAD Frederic <address@hidden>
Hi everybody,
This is the fifth version of this RFC (see the changes below).
Those are the two first patch-set we have been worked on for reverse
execution.
The first part is fully reviewed except the "icount: introduce icount
timer"
patch maybe we can merge them?
The first series:
icount: put icount variables into TimerState.
migration: migrate icount fields.
migration: make qemu_savevm_state public.
icount: introduce icount timer.
icount: check for icount clock deadline when cpu loop exits.
icount: make icount extra computed on icount clock as well.
timer: add cpu_icount_to_ns function.
are various preparation patches for reverse execution.
The last patches:
trace-events: add reverse-execution events.
introduce reverse execution mechanism.
gdbstub: allow reverse execution in gdb stub.
cpu-exec: trigger a debug request when rexec stops.
cexe: synchronize icount on the next event.
cexe: allow to enable reverse execution.
are reverse execution introduction.
They can be clone at: git://git.greensocs.com/qemu_cexe.git:cexe_2_3_v5
The third series will be sent as soon as possible and have some
issues with
QEMU's thread as it use fork.
This implementation of reverse execution works with instruction
counting:
A new clock is implemented which is icount clock. It grows each time an
instruction is executed and is totally independant of host clock.
Snapshots are taken regularly (based on icount clock) with help of
migration
code and written on the disk.
When user wants to use reverse-stepi:
* Last snapshot is reloaded.
* A stop callback is created to be triggered at the previous
instruction.
This stop callback generates a debug exception so QEMU stops in debug
mode.
Command line:
* -cexe option is added to enable reverse execution, it needs icount 1.