Re: [Qemu-devel] [RFC PATCH v5 00/13] Reverse execution.

[Frederic Konrad <fred.konrad@greensocs.com>]

On 25/06/2014 17:43, Paolo Bonzini wrote:
> Il 25/06/2014 17:19, fred.konrad@greensocs.com ha scritto:
>> From: KONRAD Frederic <fred.konrad@greensocs.com>
>>
>> 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.
>
> What does -cexe stand for?
>
> There was a patch on the list to convert -icount to QemuOpts, could 
> you adopt that and add a cexe suboption?

Hi,

You mean adding cexe as a suboption of icount?

Is both option related?
I mean reverse execution needs icount but I think it doesn't make sense 
to make it as icount suboption?

But I can convert cexe option as a QemuOpts.

Thanks,
Fred

>
> Paolo