Re: Problems using xl migrate

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 25/11/2014 22:16, M A Young wrote:
>
>
> On Tue, 25 Nov 2014, Wei Liu wrote:
>
>> On Tue, Nov 25, 2014 at 08:52:00AM +0000, M A Young wrote:
>> [...]
>>>>
>>>> And the said patch has been applied (3460eeb3fc2) so we're fine.
>>>
>>> However that doesn't fix my crash. I tried with it applied and still
>>> saw the
>>> crash. I also tried 4.5-rc1 (without XSM to avoid my other issue)
>>> and that
>>> crashed as well.
>>>
>>
>> And the log is still the same? If the crash happens in different
>> location it might be another bug.
>
> Yes, it is the same crash. Going back to the dprintf command,
>                 DPRINTF("************** pfn=%lx type=%lx gotcs=%08lx "
>                         "actualcs=%08lx\n", pfn, pagebuf->pfn_types[pfn],
>                         csum_page(region_base + i * PAGE_SIZE),
>                         csum_page(buf));
> what does pagebuf->pfn_types[pfn] actually mean and how does it relate
> to the type= it matches. I suspect it should be something else, eg.
> pfn_type[pfn] which would give the page type corresponding to pfn.
>
>     Michael Young

Eugh - this code is horrible.  (The migration v2 code is so much nicer).

"pagebuf->pfn_types[pfn]" is completely bogus in this context, and
should indeed be "pfn_type[pfn]" instead.  The pagebuf->pfn_types[]
array is up to 1024 entries long.

Having said that, it is my firm opinion that verify mode is useless for
anyone who isn't actively developing a migration stream (and even then,
less useful than it would appear to be).  I would skip the "--debug", as
I don't believe it will help you at all in tracking down your issue.

~Andrew