New: Nested Virtualisation with KVM on Intel and AMD processors: L2 unreachable
https://bugzilla.kernel.org/show_bug.cgi?id=64801
Bug ID: 64801
Summary: Nested Virtualisation with KVM on Intel and AMD
processors: L2 unreachable
Product: Virtualization
Version: unspecified
Kernel Version: 3.12
Hardware: x86-64
OS: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: kvm
Assignee: [email protected]
Reporter: [email protected]
Regression: No
With the recent kernel version(s) it seems to be impossible to reach an L2 guest. The issues sometimes even render the L0 machine unusable, and hence could be considered relevant to system security.
On three machines, the combination of KVM 1.2 and Linux 3.12 produces the following results when invoking the L2 VM:
* Intel Core i5 680: register dump
* Intel Core i7 M620: "nested_vmx_run: VMCS MSR_{LOAD,STORE} unsupported"
* AMD Athlon X2 3800+: "skip emulated instructions" messages thrown over all host ttys
On another machine, AMD Athlon II X2 240e which runs Linux 3.2.0 as host with KVM 1.1 and Linux 3.9.0 as guests, L2 can be reached. Booting the test setup from above with Linux 3.12 on all levels for comparing the results was not yet possible. The test setup consists of a minimal textmode VM which nests itself twice and contains some extra configuration for L0 for hardware support. Both SMP and single-core configurations seem to show the same behaviour.
Kernel 3.12 host (L0) minimal configuration; may need tweaks depending on the hardware in use:
Kernel 3.12 guest (L1+L2) minimal configuration:
Complete L0 test image (~800 MB) with extlinux as bootloader; may need root= and kvm_intel.nested=1 parameters, or PROMPT 1 in extlinux.conf; login is root, password is demo:
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[Bug 64801] Nested Virtualisation with KVM on Intel and AMD processors: L2 unreachable
https://bugzilla.kernel.org/show_bug.cgi?id=64801
--- Comment #1 from josef <[email protected]> ---
On the AMD Athlon II X2 240e machine, the results from above have now basically been reproduced with the L0 test image. Again, it was able to boot into L2, but not into L3. When attempting to do so, kvm outputs "vcpu0 unhandled rdmsr:0xc0000103". Afterwards, it just hangs and can be interrupted.
Now there are four different machines with four different error symptomes.
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