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Thread: Ubuntu Server KVM error - CPU does not support

  1. #1
    Join Date
    Mar 2020
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    3

    Ubuntu Server KVM error - CPU does not support

    Hi Everyone,

    I'm hoping someone can help a complete rookie here. Stuck working from home so I'm trying to learn something completely new.

    I'm trying to setup Ubuntu Server 18.04.4 on my Windows 10 machine.

    I have managed to install 18.04.4 on a virtualbox machine and can access the server within the console. Trying to use multipass to setup a couple of vm's on the server but get an error saying my CPU does not support KVM extensions.

    I have a Aorus Master X570 motherboard, AMD 3700X CPU, 64GB RAM. I went into the BIOS and enabled SVM.

    Am I out of luck or just not smart enough to figure this out?

    Thanks,
    Kevin
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  2. #2
    Join Date
    Mar 2020
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    3

    Re: Ubuntu Server KVM error - CPU does not support

    A couple of BIOS screenshots in case that helps.
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  3. #3
    Join Date
    Apr 2011
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    Mystletainn Kick!
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    Re: Ubuntu Server KVM error - CPU does not support

    You're running into the same or similar issue as this user: https://ubuntuforums.org/showthread.php?t=2439106
    The same rules of nested virtualization should apply.
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  4. #4
    Join Date
    Feb 2011
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    Coquitlam, B.C. Canada
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    2,795
    Distro
    Ubuntu Development Release

    Re: Ubuntu Server KVM error - CPU does not support

    It used to be trivial to nest KVM/QEMU vm's. Then it got harder, but still relatively easy a few years ago, as one had to remember to set `/sys/module/kvm_intel/parameters/nested` in the VM.
    However, now I can't seem to figure it out (my test server computers are 20.04 development already), as things seem to have changed yet again and `/sys/module/kvm_intel/parameters/nested` doesn't even exist on my VM.

    However, I observe that the VM's default CPU has changed, and seems to now be pathetic ("kvm-ok" says no). So I changed it to "host-passthrough" and now everything seems to be fine (("kvm-ok" says yes) and:

    Code:
    doug@serv-ff:~$ cat /sys/module/kvm_intel/parameters/nested
    Y
    Although I have yet to actually try to install a VM within that VM.

    By the way, I used "virsh edit" and changed this:

    Code:
      <cpu mode='custom' match='exact' check='partial'>
        <model fallback='allow'>Westmere-IBRS</model>
      </cpu>
    to this:
    Code:
      <cpu mode='host-passthrough' check='none'/>
    EDIT: I installed a 20.04 server VM quest on my 20.04 server VM quest on my 20.04 server host.
    Last edited by Doug S; 1 Week Ago at 01:40 AM.
    Any follow-up information on your issue would be appreciated. Please have the courtesy to report back.

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