Re: Problems using xl migrate

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

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.

~Andrew