"Hardware-assisted virtualization is not enabled on this host" even though platform:exp-nested-hvm=true is set

stormi

Noted! If this happens on our hardware too, this will be very annoying for our own virtual XCP-ng that we use all the time for development and testing.

abudef

olivierlambert Thank you very much for the impeccable support and fast communication

I tested again today and the problem is always on the host side, regardless of the type of guest. This corrects some of my hasty information above.

stormi

abudef said in "Hardware-assisted virtualization is not enabled on this host" even though platform:exp-nested-hvm=true is set:

I tested again today and the problem is always on the host side, regardless of the type of guest. This corrects some of my hasty information above.

What do you mean? Can you give examples?

abudef

stormi If the host is on version 8.3 with Xen 4.17, nested virtualization does not work on any guest. If version 8.3 with Xen 4.17 is on a guest, but the host is running version 8.2.1 or an out-of-date 8.3 (Xen 4.13), it doesn't matter and nested guest virtualization works.

stormi

abudef In the second case, do you mean there's:

8.2.1 host running a nested 8.3 (Xen 4.17) VM running itself a Nested XCP-ng? (so nested inside nested)

abudef

stormi That's not quite what I meant. The point is that if the host is 8.3/4.17, then virtualization is not working on its guest and therefore no other nested guest can be started on this guest. And actually, yes, if 8.3/4.17 appears somewhere in the cascade of nested hosts, then nested virtualization will no longer work on its guest.

olivierlambert

abudef Can you try this on a shutdown VM:

Disable nested from the VM/Advanced tab
xe vm-param-set platform:nested_virt=true uuid=<VM UUID>
Start the VM

olivierlambert

It seems we also need to modify some other bits, stand by.

abudef

Disable nested from the VM/Advanced tab
xe vm-param-set platform:nested_virt=true uuid=<VM UUID>
Start the VM

...unfortunately it didn't work, I assume because...

It seems we also need to modify some other bits

Andrew

olivierlambert On XCP 8.3/Xen 4.17 the whole vmx option is missing from any VM's CPU.... Waiting for the other bits...

olivierlambert

Yes, that's exactly the missing piece, but it has to be computed from the hex string on the pool platform CPU.

abudef

As expected, the same problem is with XenServer 8/4.17

abudef

olivierlambert stormi Please do you have any idea when this problem might be resolved? The question is how to deal with the test lab, whether to wait, because a secondary problem is that the nested VMs cannot be migrated elsewhere from the affected virtualized XCP-ng hosts.

vm.migrate
{
  "vm": "654cc5c6-7e50-fc28-ecc4-fe46929905b2",
  "mapVifsNetworks": {
    "2db4235a-345f-f286-4172-77dab4e198fe

": "8e969c1a-cafa-7ac0-504d-cf5cd19ef1e4

"
  },
  "migrationNetwork": "8e969c1a-cafa-7ac0-504d-cf5cd19ef1e4

",
  "sr": "a25ba333-a1a5-f22f-c337-0ec662e835ed",
  "targetHost": "ca60fce7-924a-45f9-a1c6-ee860952e6aa"
}
{
  "code": "NO_HOSTS_AVAILABLE",
  "params": [],
  "task": {
    "uuid": "57fe6efb-569e-3fa3-a345-d43377260884

",
    "name_label": "Async.VM.migrate_send",
    "name_description": "",
    "allowed_operations": [],
    "current_operations": {},
    "created": "20240510T10:45:50Z",
    "finished": "20240510T10:45:51Z",
    "status": "failure",
    "resident_on": "OpaqueRef:99de1bb8-8e7f-e79a-d7f9-5d84c2c09a73",
    "progress": 1,
    "type": "<none/>",
    "result": "",
    "error_info": [
      "NO_HOSTS_AVAILABLE"
    ],
    "other_config": {},
    "subtask_of": "OpaqueRef:NULL",
    "subtasks": [],
    "backtrace": "(((process xapi)(filename ocaml/xapi/xapi_vm_placement.ml)(line 106))((process xapi)(filename ocaml/xapi/message_forwarding.ml)(line 1453))((process xapi)(filename ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml)(line 24))((process xapi)(filename ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml)(line 39))((process xapi)(filename ocaml/xapi/helpers.ml)(line 1506))((process xapi)(filename ocaml/xapi/message_forwarding.ml)(line 1445))((process xapi)(filename ocaml/xapi/message_forwarding.ml)(line 2537))((process xapi)(filename ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml)(line 24))((process xapi)(filename ocaml/libs/xapi-stdext/lib/xapi-stdext-pervasives/pervasiveext.ml)(line 39))((process xapi)(filename ocaml/xapi/message_forwarding.ml)(line 2559))((process xapi)(filename ocaml/xapi/rbac.ml)(line 189))((process xapi)(filename ocaml/xapi/rbac.ml)(line 198))((process xapi)(filename ocaml/xapi/server_helpers.ml)(line 75)))"
  },
  "message": "NO_HOSTS_AVAILABLE()",
  "name": "XapiError",
  "stack": "XapiError: NO_HOSTS_AVAILABLE()
    at Function.wrap (file:///opt/xo/xo-builds/xen-orchestra-202405091612/packages/xen-api/_XapiError.mjs:16:12)
    at default (file:///opt/xo/xo-builds/xen-orchestra-202405091612/packages/xen-api/_getTaskResult.mjs:11:29)
    at Xapi._addRecordToCache (file:///opt/xo/xo-builds/xen-orchestra-202405091612/packages/xen-api/index.mjs:1029:24)
    at file:///opt/xo/xo-builds/xen-orchestra-202405091612/packages/xen-api/index.mjs:1063:14
    at Array.forEach (<anonymous>)
    at Xapi._processEvents (file:///opt/xo/xo-builds/xen-orchestra-202405091612/packages/xen-api/index.mjs:1053:12)
    at Xapi._watchEvents (file:///opt/xo/xo-builds/xen-orchestra-202405091612/packages/xen-api/index.mjs:1226:14)"
}

(targetHost above is a common native XCP-ng host)

Andrew

abudef olivierlambert stormi Ok, so we can't hot migrate a VM from 8.3 back to 8.2.... I get it... Cold migration fails also, I almost understand why it won't work because there might be features missing. Then why does Warm migration work?

Can normal cold migration be forced to work? May be as a check box/warning option that features might not be available (like TPM)?

olivierlambert

Andrew No, migration is always forward compatible, not backward. You can use warm migration in XO instead (or backup delta/restore).

olivierlambert

abudef No. We are discussing internally to see what would be the best approach.

abudef

Hello olivierlambert, curiosity prevents me from not asking if you have reached any conclusion or solution yet. Thank you in advance for revealing the hot news

olivierlambert

Hi,

It's not on the top priority list as right now, as 8.3 is coming closer and especially this Friday there's XO 5.95.
However, next week, we are at the Xen Summit, so that will be the occasion to discuss with both Vates (andSmv marcungeschikts ...) but also Xen upstream directly

abudef

Hi, did you come to any new findings and conclusions at the Xen Summit?

olivierlambert

We re asked upstream about this, no feedback yet.