** Changed in: linux (Ubuntu Bionic)
       Status: In Progress => Fix Committed

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https://bugs.launchpad.net/bugs/1741655

Title:
  Regression: KVM no longer supports Intel CPUs without Virtual NMI

Status in linux package in Ubuntu:
  Fix Committed
Status in linux source package in Artful:
  In Progress
Status in linux source package in Bionic:
  Fix Committed

Bug description:
  == SRU Justification ==
  The following mainline commit introduced a regression in v4.12-rc1:
  2c82878b0cb3 ("KVM: VMX: require virtual NMI support")

  This regression caused the kvm-intel module fail to load with the following 
error:
  "modprobe: ERROR: could not insert 'kvm_intel': Input/output error"

  This error would happen because suppor for CPUs without virtual NMI was 
removed
  by commit 2c82878b0cb3.

  Mainline commit 8a1b43922d0d fixes this regression and was added to
  mainline in v4.15-rc1.

  
  == Fix ==
  commit 8a1b43922d0d1279e7936ba85c4c2a870403c95f
  Author: Paolo Bonzini <pbonz...@redhat.com>
  Date:   Mon Nov 6 13:31:12 2017 +0100

      kvm: vmx: Reinstate support for CPUs without virtual NMI

  == Regression Potential ==
  Low.  This patch fixes a current regression.  It was cc'd to upstream stable
  so had additional upstream review.


  ## Original Bug Description ##
  Since upgrading from zesty to artful, I'm not longer able to use KVM on my 
server:
  # modprobe kvm-intel
  modprobe: ERROR: could not insert 'kvm_intel': Input/output error

  Searching tells me this is caused by requiring Virtual NMI support[1]

  Running the script provided on the mailing list[1] to check virtualization 
features confirms my CPU (Xeon E5345) doesn't support Virtual NMIs:
  # python features.py | grep NMI
    NMI exiting                              yes
    Virtual NMIs                             no
    NMI-window exiting                       no

  Virtual NMI support was required in v4.12[1] and later reverted in
  v4.14.3[2] as some models (including Xeons) don't support it, even if
  others with the same core do.

  [1] https://bugzilla.redhat.com/show_bug.cgi?id=1490803
  [2] https://lkml.org/lkml/2017/8/7/231
  [3] 
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/arch/x86/kvm/vmx.c?h=linux-4.13.y&id=2c82878b0cb38fd516fd612c67852a6bbf282003
  [4] 
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/arch/x86/kvm/vmx.c?h=linux-4.14.y&id=a77360e989f3dc06e4f177a0837d533d13a20d91

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