[v1] KVM: nVMX: Adjust VMPTRLD/VMPTRST behavior with active eVMCS

[PATCH 0/4] KVM: nVMX: Adjust VMPTRLD/VMPTRST behavior with active eVMCS

Vitaly Kuznetsov posted 4 patches 1 month, 2 weeks ago

Diff against v2 v3 v4
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arch/x86/kvm/vmx/nested.c                     | 22 +++++++++++++------
tools/testing/selftests/kvm/include/x86/vmx.h |  6 -----
.../testing/selftests/kvm/x86/hyperv_evmcs.c  | 18 ++++++++++-----
3 files changed, 28 insertions(+), 18 deletions(-)

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[PATCH 0/4] KVM: nVMX: Adjust VMPTRLD/VMPTRST behavior with active eVMCS

Posted by Vitaly Kuznetsov 1 month, 2 weeks ago

It was reported (https://bugzilla.kernel.org/show_bug.cgi?id=221841) that
KVM's emulation of VMPTRLD/VMPTRST instructions when Enlightened VMCS is
active is sub-optimal: returning '1' does not make the L1 guest skip the
instruction so a hang is likely to happen. While TLFS does not really
specify the expected behavior, genuine Hyper-V seems to return #UD for
VMPTRLD and eVMCS pointer for VMPTRST. Alter the behavior in KVM and check
it in selftests.

Note: this is not a security issue. Misbehaving L1 can only do self-harm
by doing VMPTRLD/VMPTRST when it also uses eVMCS.

Vitaly Kuznetsov (4):
  KVM: nVMX: Make VMPTRLD result in #UD when eVMCS is used
  KVM: nVMX: Make VMPTRST return eVMCS GPA when it is used
  KVM: selftests: Adapt to the updated VMPTRST behavior when eVMCS is
    used
  KVM: selftests: Check VMPTRLD with active eVMCS

 arch/x86/kvm/vmx/nested.c                     | 22 +++++++++++++------
 tools/testing/selftests/kvm/include/x86/vmx.h |  6 -----
 .../testing/selftests/kvm/x86/hyperv_evmcs.c  | 18 ++++++++++-----
 3 files changed, 28 insertions(+), 18 deletions(-)

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2.55.0