[PATCH v4 0/9] KVM: SVM: Fixes for VMCB12 checks and mapping

[Yosry Ahmed]

Jim pointed out that VMRUN/VMLOAD/VMSAVE injecting a #GP when the vmcb12
GPA is valid but not mappable is not architectural [1]. The series
handles them as emulation failures and (mostly) exits to userspace
instead. It also fixes the checks performed on the vmcb12 GPA (i.e. RAX)
in a few places.

Note that there's a few other bugs that this series leaves alone, mostly
to keep it focused on fixing the non-architectrual #GPs, this includes:
- KVM synthesizing #VMEXIT(VMLOAD/VMSAVE) to L1 when intercepting #GP
  from L2 on VMLOAD/VMSAVE, even if L1 does not intercept VMLOAD/VMSAVE
  (e.g. VLS enabled).
- KVM not respecting priority of #GP vs. #UD when EFER.SVME is disabled
  by the guest.

However, the series documents these bugs with FIXMEs so that they can
hopefully be fixed up later.

v3 -> v4:
- Fix the RAX check in the emulator instead of dropping it [Paolo].
- Add refactoring of SVM instructions on #GP intercept to facilitate
  following fixes.
- Use kvm_register_read() to handle 32-bit correctly and avoid false
  negatives.
- Do #UD and #GP checks before synthesizing #VMEXIT to L1 when KVM
  intercepts #GP on SVM instruction in L2.
- Update changelogs.

v3: https://lore.kernel.org/kvm/20260306210900.1933788-1-yosry@xxxxxxxxxx/

[1]https://lore.kernel.org/kvm/CALMp9eSMtzDJn7tGtbj=zLYpcU7Tc7XjcWBRZH7Aa5YihSmN7g@xxxxxxxxxxxxxx/

Yosry Ahmed (9):
  KVM: SVM: Properly check RAX in the emulator for SVM instructions
  KVM: SVM: Refactor SVM instruction handling on #GP intercept
  KVM: SVM: Properly check RAX on #GP intercept of SVM instructions
  KVM: SVM: Move RAX legality check to SVM insn interception handlers
  KVM: SVM: Check EFER.SVME and CPL on #GP intercept of SVM instructions
  KVM: SVM: Treat mapping failures equally in VMLOAD/VMSAVE emulation
  KVM: nSVM: Fail emulation of VMRUN/VMLOAD/VMSAVE if mapping vmcb12
    fails
  KVM: selftests: Rework svm_nested_invalid_vmcb12_gpa
  KVM: selftests: Drop 'invalid' from svm_nested_invalid_vmcb12_gpa's
    name

 arch/x86/kvm/emulate.c                        |   3 +-
 arch/x86/kvm/kvm_emulate.h                    |   2 +
 arch/x86/kvm/svm/nested.c                     |  12 +-
 arch/x86/kvm/svm/svm.c                        | 107 +++++------
 arch/x86/kvm/x86.c                            |   6 +
 tools/testing/selftests/kvm/Makefile.kvm      |   2 +-
 .../kvm/x86/svm_nested_invalid_vmcb12_gpa.c   |  98 ----------
 .../selftests/kvm/x86/svm_nested_vmcb12_gpa.c | 176 ++++++++++++++++++
 8 files changed, 244 insertions(+), 162 deletions(-)
 delete mode 100644 tools/testing/selftests/kvm/x86/svm_nested_invalid_vmcb12_gpa.c
 create mode 100644 tools/testing/selftests/kvm/x86/svm_nested_vmcb12_gpa.c


base-commit: 3d6cdcc8883b5726513d245eef0e91cabfc397f7
-- 
2.53.0.851.ga537e3e6e9-goog