Re: staging: unable to restore HVM with Viridian param set

[Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>]

n 01/02/2021 22:57, Andrew Cooper wrote:
> On 01/02/2021 22:51, Tamas K Lengyel wrote:
>> Hi all,
>> trying to restore a Windows VM saved on Xen 4.14 with Xen staging results in:
>>
>> # xl restore -p /shared/cfg/windows10.save
>> Loading new save file /shared/cfg/windows10.save (new xl fmt info 
>> 0x3/0x0/1475)
>>  Savefile contains xl domain config in JSON format
>> Parsing config from <saved>
>> xc: info: Found x86 HVM domain from Xen 4.14
>> xc: info: Restoring domain
>> xc: error: set HVM param 9 = 0x0000000000000065 (17 = File exists):
>> Internal error
>> xc: error: Restore failed (17 = File exists): Internal error
>> libxl: error: libxl_stream_read.c:850:libxl__xc_domain_restore_done:
>> restoring domain: File exists
>> libxl: error: libxl_create.c:1581:domcreate_rebuild_done: Domain
>> 8:cannot (re-)build domain: -3
>> libxl: error: libxl_domain.c:1182:libxl__destroy_domid: Domain
>> 8:Non-existant domain
>> libxl: error: libxl_domain.c:1136:domain_destroy_callback: Domain
>> 8:Unable to destroy guest
>> libxl: error: libxl_domain.c:1063:domain_destroy_cb: Domain
>> 8:Destruction of domain failed
>>
>> Running on staging 419cd07895891c6642f29085aee07be72413f08c
> 
> CC'ing maintainers and those who've edited the code recently.
> 
> What is happening is xl/libxl is selecting some viridian settings,
> applying them to the domain, and then the migrations stream has a
> different set of viridian settings.
> 
> For a migrating-in VM, nothing should be set during domain build. 
> Viridian state has been part of the migrate stream since before mig-v2,
> so can be considered to be everywhere relevant now.

The fallout is likely from my changes that modified default set of viridian
settings. The relevant commits:
983524671031fcfdb24a6c0da988203ebb47aebe
7e5cffcd1e9300cab46a1816b5eb676caaeed2c1

The same config from migrated domains now implies different set of viridian
extensions then those set at the source side. That creates inconsistency in
libxl. I don't really know how to address it properly in libxl other than
don't extend the default set ever.

Igor