[Qemu-devel] Saving and restoring CPU state

[Qemu-devel] Saving and restoring CPU state

[eady]

I'm experimenting a bit with QEMU and am in need of a way to save and 
restore X86 CPU state including the pc so that the processor state can 
be rolled back to re execute from the previous point. I've found the 
functions "cpu_x86_fsave" and "cpu_restore_state" but do not understand 
them well enough to use them. Does anyone have tips on how to store the 
processor state in an auxiliary data structure and then restore it at a 
later point?

Thanks
Nuri

[Qemu-devel] Saving and restoring CPU state

[eady]

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I'm still looking for any suggestions on how to save and restore the 
target cpu state from within a custom instruction in op.c. I basically 
want a custom instruction to save the cpu state to a data structure and 
then continue on normally, a second custom instruction would then be 
used to restore the cpu state from the saved data structure at a later 
time thereby rolling back the execution of the cpu. I've tried saving 
and restoring env->eip within my custom instructions but this has no effect.

Thanks,
Nuri

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From: eady <eady@wisc.edu>
To: qemu-devel@nongnu.org
Subject: [Qemu-devel] Saving and restoring CPU state
Date: Sun, 08 Apr 2007 16:38:14 -0500
Message-ID: <461960C6.8010904@wisc.edu>

I'm experimenting a bit with QEMU and am in need of a way to save and 
restore X86 CPU state including the pc so that the processor state can 
be rolled back to re execute from the previous point. I've found the 
functions "cpu_x86_fsave" and "cpu_restore_state" but do not understand 
them well enough to use them. Does anyone have tips on how to store the 
processor state in an auxiliary data structure and then restore it at a 
later point?

Thanks
Nuri

Re: [Qemu-devel] Saving and restoring CPU state

[Rob Landley]

On Thursday 12 April 2007 12:16 pm, eady wrote:
> I'm still looking for any suggestions on how to save and restore the 
> target cpu state from within a custom instruction in op.c. I basically 
> want a custom instruction to save the cpu state to a data structure and 
> then continue on normally, a second custom instruction would then be 
> used to restore the cpu state from the saved data structure at a later 
> time thereby rolling back the execution of the cpu. I've tried saving 
> and restoring env->eip within my custom instructions but this has no effect.

How do you roll back all the writes to memory and interactions with devices 
the processor may have done?

Saving and restoring _just_ the processor state is what setjmp/longjmp does, 
and there's all sorts of restrictions on its' use...

Rob
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Penguicon 5.0 Apr 20-22, Linux Expo/SF Convention.  Bruce Schneier, Christine 
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Re: [Qemu-devel] Saving and restoring CPU state

[andrzej zaborowski]

On 18/04/07, Rob Landley <rob@landley.net> wrote:
> On Thursday 12 April 2007 12:16 pm, eady wrote:
> > I'm still looking for any suggestions on how to save and restore the
> > target cpu state from within a custom instruction in op.c. I basically
> > want a custom instruction to save the cpu state to a data structure and
> > then continue on normally, a second custom instruction would then be
> > used to restore the cpu state from the saved data structure at a later
> > time thereby rolling back the execution of the cpu. I've tried saving
> > and restoring env->eip within my custom instructions but this has no effect.
>
> How do you roll back all the writes to memory and interactions with devices
> the processor may have done?
>
> Saving and restoring _just_ the processor state is what setjmp/longjmp does,
> and there's all sorts of restrictions on its' use...

Saving and restoring just (part of) the processor state kindof is done
by i386 instructions like syscall/sysret, sysenter/sysexit, SMM/RSM
stuff and other instructions. Have a look at target-i386/helper.c

HTH,
Andrzej