*** This bug is a duplicate of bug 1778854 ***
    https://bugs.launchpad.net/bugs/1778854

Public bug reported:

Hi,
I have run into this and I'm not entirely sure if it is an error or just not 
supported.
I'll file the bug and would ask for a check and answer by the kernel Team and 
IBM about it.

On power you can never load the usual kvm_hv module in a guest.
 $ sudo modprobe kvm_hv
 modprobe: ERROR: could not insert 'kvm_hv': No such device

That is normal and expected.
But on a Power9 system I can neither load kvm_pr which was usually the way to 
go for nested KVM.

$ sudo modprobe kvm_pr
modprobe: ERROR: could not insert 'kvm_pr': Input/output error

There is no error whatsoever in dmesg when triggering this.
>From libvirt the guest is defined with all defaults - see 
>http://paste.ubuntu.com/p/2r34SG6pq6/

That gives the guest CPU this guest view:
cat /proc/cpuinfo 
processor       : 0
cpu             : POWER9 (architected), altivec supported
clock           : 2134.000000MHz
revision        : 2.2 (pvr 004e 1202)

timebase        : 512000000
platform        : pSeries
model           : IBM pSeries (emulated by qemu)
machine         : CHRP IBM pSeries (emulated by qemu)
MMU             : Radix

Nothing obvious here, also the module exists and seems normal to me:
$ modinfo kvm_pr
filename:       /lib/modules/4.17.0-6-generic/kernel/arch/powerpc/kvm/kvm-pr.ko
alias:          devname:kvm
alias:          char-major-10-232
license:        GPL
srcversion:     2472883ADEEBC51508B6BF4
depends:        kvm
intree:         Y
name:           kvm_pr
vermagic:       4.17.0-6-generic SMP mod_unload mprofile-kernel relocatable 
sig_id:         PKCS#7
signer:         
sig_key:        
sig_hashalgo:   md4
signature:      30:82...

Current kernel is From Cosmic (as that is what I test for atm):
4.17.0-6-generic

If I start the guest with the "least virtual" cpu via
  <cpu mode='host-passthrough' check='none'/>

I get no difference in /proc/cpuinfo from the guest nor does the problem
change.

So is there a special constraint to Power9, is it the cosmic kernel,
something else - would be great if there would be some advice on this.

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1786740

Title:
  kvm_pr can't load on power9

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