[Xen-devel] live migration from new platform to old platform

["Hao, Xudong" <xudong.hao@xxxxxxxxx>]

Does anyone experience for HVM live migration from new generation platform to 
old generation platform? For X86 got a failure from Broadwell to Haswell, both 
platforms used same Xen version 4.7.0 RC3.

[root@bdw-ep1 feng]# xl migrate 21 hsw-ep1 
...
migration target: Ready to receive domain.
Saving to migration stream new xl format (info 0x3/0x0/1537) Loading new save 
file <incoming migration stream> (new xl fmt info 0x3/0x0/1537)  Savefile 
contains xl domain config in JSON format Parsing config from <saved>
xc: info: Saving domain 21, type x86 HVM
xc: info: Found x86 HVM domain from Xen 4.7
xc: info: Restoring domain
xc: error: Unable to restore HVM context (1 = Operation not permitted): 
Internal error
xc: error: Restore failed (1 = Operation not permitted): Internal error
libxl: error: libxl_stream_read.c:852:libxl__xc_domain_restore_done: restoring 
domain: Operation not permitted
libxl: error: libxl_create.c:1220:domcreate_rebuild_done: cannot (re-)build 
domain: -3
libxl: error: libxl.c:1564:libxl__destroy_domid: non-existant domain 31
libxl: error: libxl.c:1523:domain_destroy_callback: unable to destroy guest 
with domid 31
libxl: error: libxl.c:1452:domain_destroy_cb: destruction of domain 31 failed 
migration target: Domain creation failed (code -3).
libxl: error: libxl_utils.c:507:libxl_read_exactly: file/stream truncated 
reading ready message from migration receiver stream
libxl: info: libxl_exec.c:118:libxl_report_child_exitstatus: migration 
transport process [20867] exited with error status 1 Migration failed, resuming 
at sender.


Guessing HVM context of some new instruction can't be restored to an old 
platform. Current Xen xl has cupid parameter parsing implement "cupid" in guest 
config, like 
cupid='host,xsave=0'
or
cpuid=[ '1:ecx=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx0' ]

So I tried to disable some new cupid in guest config, both of the two below 
method doesn't work, the HVM guest didn't disable those cupid such as "hle, 
rtm, rdseed...".
cpuid='host,3dnowprefetch=0,hle=0,rtm=0,rdseed=0,adx=0,smap=0'
cpuid=['7:ebx=xxxxxxxxxxx000xxxxxx0xxxxxx0xxxx']

From function libxl_cpuid_parse_config() of tools/libxl/libxl_cpuid.c, only 
some cupid are implemented. Feature lacking issue?

Best Regards,
Xudong


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