Re: [PATCH v2 5/5] KVM: selftests: x86: Add a test for KVM_CAP_X86_VMWARE_HYPERCALL

[Sean Christopherson <seanjc@google.com>]

On Tue, Apr 22, 2025, Zack Rusin wrote:
> Add a testcase to exercise KVM_CAP_X86_VMWARE_HYPERCALL and validate
> that KVM exits to userspace on hypercalls and registers are correctly
> preserved.
> 
> Signed-off-by: Zack Rusin <zack.rusin@broadcom.com>
> Cc: Doug Covelli <doug.covelli@broadcom.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Shuah Khan <shuah@kernel.org>
> Cc: Sean Christopherson <seanjc@google.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Joel Stanley <joel@jms.id.au>
> Cc: Zack Rusin <zack.rusin@broadcom.com>
> Cc: Isaku Yamahata <isaku.yamahata@intel.com>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: linux-kernel@vger.kernel.org
> Cc: kvm@vger.kernel.org
> Cc: linux-kselftest@vger.kernel.org
> ---
>  tools/include/uapi/linux/kvm.h                |   3 +
>  tools/testing/selftests/kvm/Makefile.kvm      |   1 +
>  .../selftests/kvm/x86/vmware_hypercall_test.c | 121 ++++++++++++++++++
>  3 files changed, 125 insertions(+)
>  create mode 100644 tools/testing/selftests/kvm/x86/vmware_hypercall_test.c
> 
> diff --git a/tools/include/uapi/linux/kvm.h b/tools/include/uapi/linux/kvm.h
> index 502ea63b5d2e..3b3ad1827245 100644
> --- a/tools/include/uapi/linux/kvm.h
> +++ b/tools/include/uapi/linux/kvm.h
> @@ -933,6 +933,9 @@ struct kvm_enable_cap {
>  #define KVM_CAP_PRE_FAULT_MEMORY 236
>  #define KVM_CAP_X86_APIC_BUS_CYCLES_NS 237
>  #define KVM_CAP_X86_GUEST_MODE 238
> +#define KVM_CAP_X86_VMWARE_BACKDOOR 239
> +#define KVM_CAP_X86_VMWARE_HYPERCALL 240
> +#define KVM_CAP_X86_VMWARE_NESTED_BACKDOOR_L0 241

Can I bribe/convince you to port KVM-Unit-Tests' x86/vmware_backdoors.c to a KVM
selftest that verifies KVM's behavior for the various combination of module param
and capability values?