Re: Question on skip_emulated_instructions()

[Avi Kivity <avi@redhat.com>]

On 04/08/2010 08:27 AM, Yoshiaki Tamura wrote:
>
> The requirement is that the guest must always be able to replay at 
> least the instruction which triggered the synchronization on the primary.


You have two choices:

  - complete execution of the instruction in both the kernel and the 
device model

This is what live migration does currently.  Any mmio and pio requests 
are completed, the last instruction is finalized, and state is saved.

  - complete execution of the instruction in the kernel, but queue 
execution of mmio/pio requests

This is more in line with what you describe.  vcpu state will be after 
the instruction, device model state will be before instruction 
completion, when you replay the queue, the device model state will be 
consistent with the vcpu state.

>   From that point of view, I think I need to transfer the vcpu state 
> before the instruction.  If I post a signal and let the guest or 
> emulator proceed, I'm not sure whether the guest on the secondary can 
> be replay as expected.  Please point out if I were misunderstanding.

If the responses to the mmio or pio request are exactly the same, then 
the replay will happen exactly the same.

-- 
error compiling committee.c: too many arguments to function