[Xen-devel] Question about region_base in xc_domain_restore of live migration

[Ming Liu <ming.aaron.liu@xxxxxxxxx>]

Hi, 
I'm studying the details about the live migration. I encounter a question when 
I read the source codes in xc_domain_save.c.
The code is:
region_base = xc_map_foreign_bulk(xc_handle, dom, PORT_READ, pfn_type, pfn_err, 
batch)
When I see xc_map_foreign_bulk function, I find that it mmap region_base to an 
address that is :
addr = mmap(NULL, (unsigned long) num << PAGE_SHIFT, port, MAP_SHARED, 
xc_handle, 0)
>From the above codes, I can know that region_base has been mapped to a block 
>of data which is the same as the size of all pages. 
After that, the there is another line of code:
rc = ioctl(xc_handle, IOCTL_PRIVCMD_MMAPBATCH_V2, &ioctlx)
Is this function used to map all machine page content to region_base?

What is the usage of region_base?
Thanks for your help. 
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