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Bug 1759205

Summary: Document how to use nested virtualization (nestedvt)
Product: Red Hat Enterprise Virtualization Manager Reporter: Patrick Toal <ptoal>
Component: DocumentationAssignee: Rolfe Dlugy-Hegwer <rdlugyhe>
Status: CLOSED CURRENTRELEASE QA Contact:
Severity: high Docs Contact:
Priority: medium    
Version: 4.3.0CC: cdoerbec, lsurette, michal.skrivanek, mtessun, rdlugyhe, srevivo
Target Milestone: ovirt-4.4.2Keywords: Documentation
Target Release: 4.4.2   
Hardware: Unspecified   
OS: Unspecified   
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Fixed In Version: Doc Type: If docs needed, set a value
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Clone Of: Environment:
Last Closed: 2020-10-05 16:49:07 UTC Type: Bug
Regression: --- Mount Type: ---
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Verified Versions: Category: ---
oVirt Team: Virt RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 1794485    
Bug Blocks:    

Description Patrick Toal 2019-10-07 15:32:11 UTC
Description of problem:

The steps required to enable nested virtualization (nestedvt) are unclear in the official documentation, and there are several references online that indicate a need for vdsm hooks that are no longer available.

A section in the official docs, explaining how to do nested virtualization would be very helpful.  

Additional info:

There is a Red Hat Mojo document on this [DOC-1194023] that could be a helpful start.

Also:
Clarify if the hook is now installed by default, or does it need to be installed on RHVH / RHEL Hosts? (as of which version?)

Comment 1 Michal Skrivanek 2020-05-07 08:06:17 UTC
We missed to document nested virtualization support we added as a TP in 4.2.z

in 4.3 and 4.4 the status of nested virtualization feature is still a Tech Preview. 

We should also mention it somewhere in Admin guide, describe how it is enabled.
it's an additional install(both on RHEL and RHVH) of vdsm-hook-nestedvt on hosts which are to support nested virtualization, and follow up with a host reboot. It can be confirmed by checking
# cat /sys/module/kvm*/parameters/nested
Y

or in Edit Host dialog, Kernel section

Comment 2 Steve Goodman 2020-05-14 07:37:46 UTC
1. In the Admin Guide, I don't see any info on how to install hooks. The closest I see is this sentence:
   
   "When a supported event occurs VDSM runs any executable hook scripts in
    /usr/libexec/vdsm/hooks/nn_event-name/ on the host in alphanumeric order." [1]
2. How does the user get the vdsm-hook-nestedvt hook in order to install it? 
   Do you need to download it from someplace? Or is it part of the 4.2, 4.3 and 4.4
   packages? Please be specific.
3. How do you enable nested virtualization using the Edit Host dialog, Kernel section? Is this instead of or in addition to installing and enabling the VDSM hook?

[1] https://access.redhat.com/documentation/en-us/red_hat_virtualization/4.4-beta/html-single/administration_guide/index#VDSM_hooks

Comment 3 Steve Goodman 2020-05-14 07:57:41 UTC
OK, I think I understand a bit better. I found the Nesterd Virtualization checkbox. It's tooltip says:

Enables or disables nested virtualization. Nested virtualization passes vmx/svm (hardware virtualization flag) to guest operating system. Requires vdsm & `nestedvt` hook.

1. Install the hook.


I found the checkbox in:

1. Computer>Hosts
2. Click a host and then click Edit.
3. Go to the Kernel pane and check the Nested Virtualization checkbox.

Comment 4 Sandro Bonazzola 2020-05-14 08:01:36 UTC
For RHEL hosts, in order to enable nested virtualization you can just install vdsm-hook-nestedvt and reboot.

For RHV-H we have a bug for adding vdsm-hook-nestedvt to the optional channel (bug #1794485). It will require an additional step on enabling the optional channel and then continue with installing the rpm.

Comment 5 Michal Skrivanek 2020-05-14 08:18:22 UTC
also check my comment (or draft version of the aricle, I can' publish it myself) in https://access.redhat.com/solutions/3543721

As for comment #2 1) - I think it's similar like e.g. https://access.redhat.com/documentation/en-us/red_hat_virtualization/4.2/html-single/administration_guide/index#Preparing_GPU_Passthrough where you need to prepare a host for some VM functionality later. Maybe a new section there (since then there's actually no VM configuration required so it really is just about doing something on the host)

Comment 7 Rolfe Dlugy-Hegwer 2020-09-28 23:33:19 UTC
*** Bug 1832721 has been marked as a duplicate of this bug. ***

Comment 8 Rolfe Dlugy-Hegwer 2020-09-28 23:57:51 UTC
*** Bug 1759342 has been marked as a duplicate of this bug. ***