Re: code read problems

[tgh <wwwwww4187@sina.com.cn>]

Thank you for your reply
I encounter other confusions,

 1)when I read the code of restore() in checkpoint.py for paravirt
 and restore() calls for the dominfo.completeRestore(),which call 
_registerWatches(), and then call refreshShutdown(),
 and in refreshShutdown(),if   elif xeninfo['shutdown']:  and  if reason 
== 'suspend' ,self._unwatchVM()will be called ,

                   if reason == 'suspend':
                       self._stateSet(DOM_STATE_SUSPENDED)
                       # Don't destroy the domain.  XendCheckpoint will do
                       # this once it has finished.  However, stop watching
                       # the VM path now, otherwise we will end up with one
                       # watch for the old domain, and one for the new.
                       self._unwatchVm()

and then ,why do we call _registerWatches() before refreshShutdown(),i 
am confused about it,
and what is the function of dominfo.completeRestore()? it 
introducedomain(),and storeDomDetails() and registerWatches()and 
,refreshShutdown(),and why should it refreshShutdown()?and is it that in 
refreshShutdown(),the old domain is cleaned and destoryed, or the new 
domain is dealt with? i am confused

2) and the code of save() in the checkpoint.py, how does the 
saveInputHandler synchronize with the XC_SAVE ?  how many times do they 
synchronize with each other？ only ,XC_SAVE sends "suspend" to 
saveInputHandler,  and then saveInputHandler  send "done" to XC_SAVE   
,is it right?                           
       def saveInputHandler(line, tochild):
           log.debug("In saveInputHandler %s", line)
           if line == "suspend":
               log.debug("Suspending %d ...", dominfo.getDomid())
               dominfo.shutdown('suspend')
               dominfo.waitForShutdown()
               dominfo.migrateDevices(network, dst, 
DEV_MIGRATE_STEP2,domain_name)
               log.info("Domain %d suspended.", dominfo.getDomid())
               dominfo.migrateDevices(network, dst, 
DEV_MIGRATE_STEP3,domain_name)
               #send signal to device model for save
               if hvm:
                   log.info("release_devices for hvm domain")
                   dominfo._releaseDevices(True)
               tochild.write("done\n")
               tochild.flush()
               log.debug('Written done')

and how many times does XC_SAVE synchronize with Handler, i read the 
code , and just find only one time ,is it right?
3) and what is the function of the dominfo.migrateDevices with 
DEV_MIGRATE_STEP2 and DEV_MIGRATE_STEP3, i read the code ,but still 
confused, does  it  put the  information of the devices into the 
checkpoint file , or what?
4) and how does xen deal with the requests of devices in the ring and 
gnttb and backend ,how does it store them? i have not find the code to 
deal with it?


could you help me

Thanks in advance



Daniel Stodden 写道:
> Hi.
>
> On Fri, 2008-02-29 at 14:44 +0800, tgh wrote:
>   
>> hi
>>   I read checkpoint code
>>   when checkpoint or migration ends,guestos continues processing by 
>> returning back from hypercall of suspend, that is ,take_machine_down() 
>> call the post_suspend() to continue ,is it right?
>>   while in post_suspend(),pfn_to_mfn_frame_list_list[] is converted by 
>> virt_to_mfn(),why do this convert? i could not find where it has been 
>> converted,and why should it be converted back?
>>     
>
> No, not converted. Re-initialized. 
>
> Please compare post_suspend() with the original initialization at system
> boot in setup_arch() (arch/x/kernel/setup-xen.c). It should come clear
> then.
>
> Observe that this is not canonicalization, because it is not the p2m,
> but a directory containing the *machine frames* *carrying* the p2m.
> Since the memory underlying the p2m has changed after resume, that
> directory needs a reset.
>
>   
>>   and in the xc_domain_restore()in the dom0,pagetable has been 
>> uncanonicalized, which is coupled with canonicalization in 
>> xc_domain_save(),is it ? ,and what is the reasons for 
>> pfn_to_mfn_frame_list_list[] virt_to_mfn in post_suspend()?
>>   could you help me
>>     
>
> Canonicalization forth and back is done by the migration code. Keeping
> the allocated frame list up to date is done by the domain itself. I do
> agree that this can be confusing indeed.
>
> hth,
> Daniel
>  
>