Re: [PATCH v2 0/9] KVM: x86: Improve the handling of debug exceptions during instruction emulation

[Sean Christopherson]

On Thu, Dec 18, 2025, Hou Wenlong wrote:
> Hou Wenlong (9):
>   KVM: x86: Capture "struct x86_exception" in
>     inject_emulated_exception()
>   KVM: x86: Set guest DR6 by kvm_queue_exception_p() in instruction
>     emulation
>   KVM: x86: Check guest debug in DR access instruction emulation
>   KVM: x86: Only check effective code breakpoint in emulation
>   KVM: x86: Consolidate KVM_GUESTDBG_SINGLESTEP check into the
>     kvm_inject_emulated_db()
>   KVM: x86: Move kvm_set_rflags() up before kvm_vcpu_do_singlestep()
>   KVM: VMX: Refresh 'PENDING_DBG_EXCEPTIONS.BS' bit during instruction
>     emulation
>   KVM: selftests: Verify guest debug DR7.GD checking during instruction
>     emulation
>   KVM: selftests: Verify 'BS' bit checking in pending debug exception
>     during VM entry
> 
>  arch/x86/include/asm/kvm-x86-ops.h            |   1 +
>  arch/x86/include/asm/kvm_host.h               |   1 +
>  arch/x86/kvm/emulate.c                        |  14 +--
>  arch/x86/kvm/kvm_emulate.h                    |   7 +-
>  arch/x86/kvm/vmx/main.c                       |   9 ++
>  arch/x86/kvm/vmx/vmx.c                        |  15 ++-
>  arch/x86/kvm/vmx/x86_ops.h                    |   1 +
>  arch/x86/kvm/x86.c                            | 116 ++++++++++--------
>  arch/x86/kvm/x86.h                            |   7 ++
>  .../selftests/kvm/include/x86/processor.h     |   3 +-
>  tools/testing/selftests/kvm/x86/debug_regs.c  |  72 ++++++++++-
>  11 files changed, 178 insertions(+), 68 deletions(-)

One goof and some nits on patch 3, but I'll fix them up when applying, i.e. no
need for a v3.  I'll probably also add some comments and elaborate on some of
the changelogs.