Re: [Xen-devel] error in xen/arch/x86/mm.c:get_page during migration

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 21.02.13 at 18:31, Olaf Hering <olaf@xxxxxxxxx> wrote:
> On Thu, Feb 21, Jan Beulich wrote:
> 
>> What you could do to get a better understanding of when this
>> happens is to add a WARN_ON() alongside the printk() (perhaps
>> such that it triggers only once for each of the two different
>> cases), and then let us look at the call trace.
> 
> It did not happen with xl.

Odd.

> Here is the output while doing xm migrate:
> ...
> (XEN) Xen call trace:
> (XEN)    [<ffff82c4c0170fb2>] get_page+0xfb/0x151
> (XEN)    [<ffff82c4c01e1d87>] get_page_from_gfn_p2m+0x17e/0x284
> (XEN)    [<ffff82c4c01098ae>] __get_paged_frame+0x5d/0x170
> (XEN)    [<ffff82c4c0109e55>] __acquire_grant_for_copy+0x494/0x6ae
> (XEN)    [<ffff82c4c010bef0>] gnttab_copy+0x53b/0x843
> (XEN)    [<ffff82c4c010e3b8>] do_grant_table_op+0x11c5/0x1b82
> (XEN)    [<ffff82c4c011502f>] do_multicall+0x227/0x444
> (XEN)    [<ffff82c4c0227f0b>] syscall_enter+0xeb/0x145
> ...
> (XEN) Xen call trace:
> (XEN)    [<ffff82c4c0170fdc>] get_page+0x125/0x151
> (XEN)    [<ffff82c4c01e1d87>] get_page_from_gfn_p2m+0x17e/0x284
> (XEN)    [<ffff82c4c01098ae>] __get_paged_frame+0x5d/0x170
> (XEN)    [<ffff82c4c0109e55>] __acquire_grant_for_copy+0x494/0x6ae
> (XEN)    [<ffff82c4c010bef0>] gnttab_copy+0x53b/0x843
> (XEN)    [<ffff82c4c010e3b8>] do_grant_table_op+0x11c5/0x1b82
> (XEN)    [<ffff82c4c011502f>] do_multicall+0x227/0x444
> (XEN)    [<ffff82c4c0227f0b>] syscall_enter+0xeb/0x145

And that's without paging or anything similar? Else I would expect
the problem to be in the interaction there. But I'll also take a look
at the grant table code assuming this is a problem even without
any enhanced memory management functionality...

Jan


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