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Re: [Xen-devel] (4.5-rc1) Problems using xl migrate



On 24/11/14 14:32, M A Young wrote:
> On Mon, 24 Nov 2014, Andrew Cooper wrote:
>
>> On 24/11/14 12:41, Wei Liu wrote:
>>> On Sat, Nov 22, 2014 at 07:24:21PM +0000, M A Young wrote:
>>>> While investigating a bug reported on Red Hat Bugzilla
>>>> https://bugzilla.redhat.com/show_bug.cgi?id=1166461
>>>> I discovered the following
>>>>
>>>> xl migrate --debug domid localhost does indeed fail for Xen 4.4 pv
>>>> (the bug
>>>> report is for Xen 4.3 hvm ) when xl migrate domid localhost works.
>>>> There are
>>>> actually two issues here
>>>>
>>>> * the segfault in libxl-save-helper --restore-domain (as reported
>>>> in the bug
>>>> above) occurs if the guest memory is 1024M (on my 4G box) and is
>>>> presumably
>>>> because the allocated memory eventually runs out
>>>>
>>>> * the segfault doesn't occur if the guest memory is 128M, but the
>>>> migration
>>>> still fails. The first attached file contains the log from a run
>>>> with xl -v
>>>> migrate --debug domid localhost (with mfn and duplicated lines
>>>> stripped out
>>>> to make the size manageable).
>>>>
>>>> I then tried xen 4.5-rc1 to see if the bug was fixed and found that xl
>>>> migrate doesn't work for me at all - see the second attached file
>>>> for the
>>>> output of xl -v migrate domid localhost .
>>>>
>>>>     Mchael Young
>>> [...]
>>>> xc: detail: delta 15801ms, dom0 95%, target 0%, sent 543Mb/s,
>>>> dirtied 0Mb/s 314 pages
>>>> xc: detail: Mapping order 0,  268; first pfn 3fcf4
>>>> xc: detail: delta 23ms, dom0 100%, target 0%, sent 447Mb/s, dirtied
>>>> 0Mb/s 0 pages
>>>> xc: detail: Start last iteration
>>>> xc: Reloading memory pages: 262213/262144  100%xc: detail: SUSPEND
>>>> shinfo 00082fbc
>>>> xc: detail: delta 17ms, dom0 58%, target 58%, sent 0Mb/s, dirtied
>>>> 1033Mb/s 536 pages
>>>> xc: detail: delta 8ms, dom0 100%, target 0%, sent 2195Mb/s, dirtied
>>>> 2195Mb/s 536 pages
>>>> xc: detail: Total pages sent= 262749 (1.00x)
>>>> xc: detail: (of which 0 were fixups)
>>>> xc: detail: All memory is saved
>>>> xc: error: Error querying maximum number of MSRs for VCPU0 (1 =
>>>> Operation not permitted): Internal error
>>> Per your description this is the output of "xl -v migrate domid
>>> localhost", so no "--debug" is involved. (Just to make sure...)
>>>
>>> This error message means a domctl fails, which should be addressed
>>> first?
>>>
>>> FWIW I tried "xl -v migrate domid localhost" for a PV guest it worked
>>> for me. :-(
>>>
>>> Is there anything I need to do to trigger this failure?
>>
>> Is XSM in use?  I can't think of any other reason why that hypercall
>> would fail with EPERM.
>
> XSM is built in (I wanted to allow the option of people using it) but
> I didn't think it was active.
>
>     Michael Young

I don't believe there is any concept of "available but not active",
which probably means that the default policy is missing an entry for
this hypercall.

Can you check the hypervisor console around this failure and see whether
a flask error concerning domctl 72 is reported?

~Andrew


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