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[Bug 1329434] Re: nested KVM fails on intel hardware - KVM: entry failed, hardware error 0x0


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

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  nested KVM fails on intel hardware - KVM: entry failed, hardware error

Status in “linux” package in Ubuntu:
  Fix Released
Status in “linux” source package in Trusty:
  Fix Committed

Bug description:
  Using nested KVM on some hypervisors doesn't work.

  [Test Case]
  A script to make this easier is posted here:

  1) enable nested KVM:
  sudo modprobe -r kvm_intel
  sudo modprobe kvm_intel nested=1
  cat /sys/module/kvm_intel/parameters/nested
  # should say Y
  2) generate an L1 guest and then generate an L2 guest inside the L1 guest
  - ensure L1 has enough memory to boot L2
  - if using libvirt you may need to edit the default bridge to use a different subnet than the L1 guest
  3) boot the L2 guest
  4) L2 guest should boot


  These three upstream patches needed to be backported to 3.13:

  * 533558bcb69ef28aff81b6ae9acda8943575319f
    - This provides necessary code changes to make backporting easier. However vmx_leave_nested function was not yet added, so that function modification was dropped.

  * b6b8a1451fc40412c57d10c94b62e22acab28f94
    - This patch is necessary in order to ensure that the L1 guest doesn't crash with just 696dfd95 applied. I had to remove mpx mentions from the cherry-pick as that feature hasn't been added yet.

  * 696dfd95ba9838327a7013e5988ff3ba60dcc8c8
    - This patch fixes the issue and was the result of the bisection. The APIC virtualization features need to be disabled as they cause L2 guests to not boot depending on the CPU.


  If the L2 guest doesn't boot you can see the log:
  sudo cat /var/log/libvirt/qemu/nested-L2.log
  KVM: entry failed, hardware error 0x0
  EAX=00000000 EBX=00000000 ECX=00000000 EDX=00000663
  ESI=00000000 EDI=00000000 EBP=00000000 ESP=00000000
  EIP=0000fff0 EFL=00000002 [-------] CPL=0 II=0 A20=1 SMM=0 HLT=0
  ES =0000 00000000 0000ffff 00009300
  CS =f000 ffff0000 0000ffff 00009b00
  SS =0000 00000000 0000ffff 00009300
  DS =0000 00000000 0000ffff 00009300
  FS =0000 00000000 0000ffff 00009300
  GS =0000 00000000 0000ffff 00009300
  LDT=0000 00000000 0000ffff 00008200
  TR =0000 00000000 0000ffff 00008b00
  GDT=     00000000 0000ffff
  IDT=     00000000 0000ffff
  CR0=60000010 CR2=00000000 CR3=00000000 CR4=00000000
  DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000 DR3=0000000000000000
  DR6=00000000ffff0ff0 DR7=0000000000000400
  Code=00 66 89 d8 66 e8 02 f7 ff ff 66 83 c4 0c 66 5b 66 5e 66 c3 <ea> 5b e0 00 f0 30 36 2f 32 33 2f 39 39 00 fc 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
   total 0
   crw-rw---- 1 root audio 116,  1 Jun 13 18:26 seq
   crw-rw---- 1 root audio 116, 33 Jun 13 18:26 timer
  AplayDevices: Error: [Errno 2] No such file or directory
  ApportVersion: 2.14.1-0ubuntu3.2
  Architecture: amd64
  ArecordDevices: Error: [Errno 2] No such file or directory
  AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
  DistroRelease: Ubuntu 14.04
  IwConfig: Error: [Errno 2] No such file or directory
  MachineType: Intel Corporation S2600WTT
  Package: linux (not installed)

   PATH=(custom, no user)
  ProcFB: 0 VESA VGA
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.13.0-24-generic root=UUID=b5d11a1d-c48f-4abf-a622-d1efe52fe97c ro
  ProcVersionSignature: User Name 3.13.0-24.46-generic 3.13.9
   linux-restricted-modules-3.13.0-24-generic N/A
   linux-backports-modules-3.13.0-24-generic  N/A
   linux-firmware                             1.127.2
  RfKill: Error: [Errno 2] No such file or directory
  Tags:  trusty uec-images
  Uname: Linux 3.13.0-24-generic x86_64
  UpgradeStatus: No upgrade log present (probably fresh install)
  UserGroups: adm audio cdrom dialout dip floppy libvirtd netdev plugdev sudo video
  _MarkForUpload: True
  dmi.bios.date: 05/06/2014
  dmi.bios.vendor: Intel Corporation
  dmi.bios.version: GRNDSDP1.86B.0030.R03.1405061547
  dmi.board.asset.tag: Base Board Asset Tag
  dmi.board.name: S2600WTT
  dmi.board.vendor: Intel Corporation
  dmi.board.version: H30334-201
  dmi.chassis.asset.tag: ....................
  dmi.chassis.type: 23
  dmi.chassis.vendor: ...............................
  dmi.chassis.version: ..................
  dmi.modalias: dmi:bvnIntelCorporation:bvrGRNDSDP1.86B.0030.R03.1405061547:bd05/06/2014:svnIntelCorporation:pnS2600WTT:pvr....................:rvnIntelCorporation:rnS2600WTT:rvrH30334-201:cvn...............................:ct23:cvr..................:
  dmi.product.name: S2600WTT
  dmi.product.version: ....................
  dmi.sys.vendor: Intel Corporation

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