[Devel] Re: [RFC][PATCH 2/4] checkpoint/restart: x86 support

Jeremy Fitzhardinge jeremy at goop.org
Mon Aug 11 09:07:35 PDT 2008


Dave Hansen wrote:
> On Sun, 2008-08-10 at 07:55 -0700, Jeremy Fitzhardinge wrote:
>   
>> Struct pt_regs is not ABI, and can (and has) changed on x86.   It's not 
>> suitable for a checkpoint structure because it only contains the 
>> registers that the kernel trashes, not all usermode registers (on i386, 
>> it leaves out %gs, for example).  asm-x86/ptrace-abi.h does define stuff 
>> that's fixed in stone; it expresses it in terms of a register array, 
>> with constants defining what element is which register.
>>     
>
> Thanks for the explanation.
>
> I just want to reduce the coding and maintenance burden here.  Xen must
> do this for partition mobility, right?  Does it define all its own
> stuff?
>   

You mean save/restore/migrate?  Yes, it defines all its own stuff.  
Checkpoint-resume on a whole VM is a rather simpler operation than a 
subset of processes.

    J

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