[PATCH v2 0/4] KVM: nVMX: Adjust VMPTRLD/VMPTRST behavior with active eVMCS

[Vitaly Kuznetsov <vkuznets@redhat.com>]

Changes since v1:
- Fix build when !CONFIG_KVM_HYPERV [Sashiko]
- Drop now-unneeded evmcs_vmptrst() [Sashiko]
- Avoid hardcoding VMPTRLD insn length in hyperv_evmcs [Sashiko], use
  KVM_ASM_SAFE framework instead [Sean]

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                     | 24 +++++++++-----
 .../testing/selftests/kvm/include/x86/evmcs.h |  8 -----
 tools/testing/selftests/kvm/include/x86/vmx.h | 22 +++++++++----
 .../testing/selftests/kvm/x86/hyperv_evmcs.c  | 31 ++++++++++++++-----
 4 files changed, 56 insertions(+), 29 deletions(-)

-- 
2.55.0