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Date: Wed, 15 May 2013 15:35:01 +0200
From: =?ISO-8859-1?Q?KONRAD_Fr=E9d=E9ric?= <fred.konrad@greensocs.com>
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Subject: Re: [Qemu-devel] [RFC] save/restore with icount enabled.
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Mark Burton <mark.burton@greensocs.com>, qemu-devel <qemu-devel@nongnu.org>

On 15/05/2013 14:50, Paolo Bonzini wrote:
> Il 15/05/2013 11:31, KONRAD Fr=E9d=E9ric ha scritto:
>> Hi,
>>
>> We are trying to do a simple save/restore on the VM with icount enable=
d.
>>
>> We saw that qemu_icount_bias and qemu_icount in cpus.c are not
>> saved/restored,
>> and icount_extra, icount_decr in CPUState neither, so the vm_clock is =
just
>> growing normally after restoring the VM is that normal?
>>
>> We think that this is making the "replay" undeterminastic, which is ba=
d for
>> reverse execution.
>>
>> Is there a good reason for them not being saved?
> No.  You can probably move icount to timers_state.  Something like
> zeroing qemu_icount in cpu_disable_ticks() is required in order to save
> qemu_icount_bias like the other members of timers_state.  There is even
> a dummy field that you can reuse to avoid the pain of adding a
> subsection to vmstate_timers. :)
>
> Paolo

Yes nice point :).

What about icount_extra and icount_decr defined in CPU_COMMON? in=20
cpu-defs.h?

     int64_t icount_extra; /* Instructions until next timer event. */   \
     /* Number of cycles left, with interrupt flag in high bit.          =
\
        This allows a single read-compare-cbranch-write sequence to test =
\
        for both decrementer underflow and exceptions. */               \
     union {                                                             =
\
         uint32_t u32;                                                   =
\
         icount_decr_u16 u16;                                            =
\
     } icount_decr;                                                      =
\

Thanks,
Fred
>> Thanks,
>> Fred
>>
>>