[Bug]: Guru Meditation VERR_SVM_UNKNOWN_EXIT when a nested KVM guest (crosvm/Cuttlefish) starts in an AMD-V nested-virtualization guest

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Évaluation

Difficulté
4/5
Temps estimé
3-5 jours
Accessibilité débutants
42/100
Type d'issue
Bug
Clarté
Plutôt claire
Activité
Active
Stack technique
c

Piste de recherche

Start in the VMM AMD-V/SVM handling, using the reported VERR_SVM_UNKNOWN_EXIT and nested-guest VMCB cache log entries as search terms; the issue does not name source files or tests. Reproduce by starting a KVM guest inside the Debian VM with nested virtualization enabled, then inspect the VM log around the SVM exit and the repeated catch-up messages. Done means the nested guest can run without the host VM entering Guru Meditation.

Rédigé par le modèle d'indexation à partir du texte de l'issue.

Description

bug
Version

7.2.20

Host OS Type

Windows

Host OS name + version

Windows 11 Pro 10.0.26200.9711 (Hyper-V/VBS disabled)

Host Architecture

x86

Guest OS Type

Linux

Guest Architecture

x86

Guest OS name + version

Debian 13 (Trixie)

Component

VMM

What happened?

The whole VM stops with VCPU6: Guru Meditation -4060 (VERR_SVM_UNKNOWN_EXIT) (state GURU_MEDITATION, rcLastExitToR3 = VERR_SVM_UNKNOWN_EXIT) when a nested KVM guest is started inside a Debian guest with Nested VT-x/AMD-V enabled. The nested guest is Android Cuttlefish (crosvm using /dev/kvm).

The log shows fNestedPaging = false in the nested-guest VMCB cache on all CPUs, and repeated TM: Giving up catch-up attempt messages before the crash.

Host: AMD Ryzen 7 5700G (Zen 3), 32 GB RAM, Windows 11 Pro 10.0.26200.9711. Hyper-V, Virtual Machine Platform and VBS are disabled; VBoxManage list hostinfo reports Processor supports nested HW virtualization: yes.

Guest: Debian 13 x86_64, 8 vCPUs, 16 GB RAM, VBoxManage modifyvm --nested-hw-virt on, Guest Additions installed, /dev/kvm present in the guest.

Likely reproducible with any KVM guest (QEMU or crosvm) started inside the VM; not specific to Cuttlefish. The attached VBox.log has usernames and the VM name scrubbed.

Relevant VBox.log excerpt 
00:26:35.411126 Changing the VM state from 'RUNNING' to 'GURU_MEDITATION'
00:26:35.411191 Console: Machine state changed to 'Stuck'
00:26:35.411812 !!         VCPU6: Guru Meditation -4060 (VERR_SVM_UNKNOWN_EXIT)
...
00:26:35.424161 CPU[5]: AMD-V info:
00:26:35.424162   HM error           = 0x0 (0)
00:26:35.424162   rcLastExitToR3     = VINF_EM_HALT
00:26:35.424168 CPU[6]: AMD-V info:
00:26:35.424168   HM error           = 0xa2 (162)
00:26:35.424169   rcLastExitToR3     = VERR_SVM_UNKNOWN_EXIT
...
00:26:35.429086 CPU[0]: HM SVM nested-guest VMCB cache
00:26:35.429099   fNestedPaging           = false
How can we reproduce this?
  1. On a Windows 11 host with an AMD CPU (Hyper-V/VBS disabled), create a Debian 13 x86_64 VM, 8 vCPUs, 16 GB RAM, and enable Nested VT-x/AMD-V (VBoxManage modifyvm <vm> --nested-hw-virt on). Confirm /dev/kvm exists in the guest.
  2. In the guest, install Android Cuttlefish 1.57.0 (cuttlefish-base and cuttlefish-user from the google/android-cuttlefish apt repo) and add your user to the kvm, cvdnetwork and render groups. Reboot.
  3. mkdir ~/cf && cd ~/cf && cvd fetch --default_build=aosp-android-latest-release/aosp_cf_x86_64_only_phone-userdebug
  4. cvd create --host_path=$HOME/cf --product_path=$HOME/cf --cpus=4 --memory_mb=6144
  5. Wait about a minute while the nested guest boots. The VM then enters Guru Meditation with VERR_SVM_UNKNOWN_EXIT.
Did you upload all of your necessary log files, screenshots, etc.?
  • Yes, I've uploaded all pertinent files to this issue.
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