Prior to commit 9245fd6b8531 ("KVM: x86: model canonical checks more
precisely"), KVM_SET_NESTED_STATE would fail if the state was captured
with L2 active, L1 had CR4.LA57 set, L2 did not, and the
VMCS12.HOST_GSBASE (or other host-state field checked for canonicality)
had an address greater than 48 bits wide.

Add a regression test that reproduces the KVM_SET_NESTED_STATE failure
conditions. To do so, the first three patches add support for 5-level
paging in the selftest L1 VM.

v1 -> v2
  Ended the page walking loops before visiting 4K mappings [Yosry]
  Changed VM_MODE_PXXV48_4K into VM_MODE_PXXVYY_4K;
    use 5-level paging when possible                       [Sean] 
  Removed the check for non-NULL vmx_pages in guest_code() [Yosry]

Jim Mattson (4):
  KVM: selftests: Use a loop to create guest page tables
  KVM: selftests: Use a loop to walk guest page tables
  KVM: selftests: Change VM_MODE_PXXV48_4K to VM_MODE_PXXVYY_4K
  KVM: selftests: Add a VMX test for LA57 nested state

 tools/testing/selftests/kvm/Makefile.kvm      |   1 +
 .../testing/selftests/kvm/include/kvm_util.h  |   4 +-
 .../selftests/kvm/include/x86/processor.h     |   2 +-
 .../selftests/kvm/lib/arm64/processor.c       |   2 +-
 tools/testing/selftests/kvm/lib/kvm_util.c    |  30 ++--
 .../testing/selftests/kvm/lib/x86/processor.c |  80 +++++------
 tools/testing/selftests/kvm/lib/x86/vmx.c     |   6 +-
 .../kvm/x86/vmx_la57_nested_state_test.c      | 134 ++++++++++++++++++
 8 files changed, 197 insertions(+), 62 deletions(-)
 create mode 100644 tools/testing/selftests/kvm/x86/vmx_la57_nested_state_test.c

-- 
2.51.1.851.g4ebd6896fd-goog

On Tue, 28 Oct 2025 15:30:38 -0700, Jim Mattson wrote:
> Prior to commit 9245fd6b8531 ("KVM: x86: model canonical checks more
> precisely"), KVM_SET_NESTED_STATE would fail if the state was captured
> with L2 active, L1 had CR4.LA57 set, L2 did not, and the
> VMCS12.HOST_GSBASE (or other host-state field checked for canonicality)
> had an address greater than 48 bits wide.
> 
> Add a regression test that reproduces the KVM_SET_NESTED_STATE failure
> conditions. To do so, the first three patches add support for 5-level
> paging in the selftest L1 VM.
> 
> [...]

Applied to kvm-x86 selftests, thanks!

[1/4] KVM: selftests: Use a loop to create guest page tables
      https://github.com/kvm-x86/linux/commit/ae5b498b8da9
[2/4] KVM: selftests: Use a loop to walk guest page tables
      https://github.com/kvm-x86/linux/commit/2103a8baf5cb
[3/4] KVM: selftests: Change VM_MODE_PXXV48_4K to VM_MODE_PXXVYY_4K
      https://github.com/kvm-x86/linux/commit/ec5806639e39
[4/4] KVM: selftests: Add a VMX test for LA57 nested state
      https://github.com/kvm-x86/linux/commit/6a8818de21d2

--
https://github.com/kvm-x86/linux/tree/next