Re: [PATCH] KVM: selftests: sync_regs_test: use KVM_SYNC_X86_VALID_FIELDS

[Sean Christopherson <seanjc@google.com>]

On Mon, May 11, 2026, Piotr Zarycki wrote:
> Use KVM_SYNC_X86_VALID_FIELDS instead of open-coding the same three
> flags, ensuring the test stays in sync with any future additions.
> 
> Signed-off-by: Piotr Zarycki <piotr.zarycki@gmail.com>
> ---
>  tools/testing/selftests/kvm/x86/sync_regs_test.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/x86/sync_regs_test.c b/tools/testing/selftests/kvm/x86/sync_regs_test.c
> index e0c52321f87c..8f9239f9d357 100644
> --- a/tools/testing/selftests/kvm/x86/sync_regs_test.c
> +++ b/tools/testing/selftests/kvm/x86/sync_regs_test.c
> @@ -79,7 +79,7 @@ static void compare_vcpu_events(struct kvm_vcpu_events *left,
>  {
>  }
>  
> -#define TEST_SYNC_FIELDS   (KVM_SYNC_X86_REGS|KVM_SYNC_X86_SREGS|KVM_SYNC_X86_EVENTS)
> +#define TEST_SYNC_FIELDS   KVM_SYNC_X86_VALID_FIELDS

Explicitly defining the set of fields to test is very deliberate.  (a) we want
to detect ABI breakage, e.g. if KVM removes a valid field.  (b) if a field is
added in the future, the test likely needs to be updated, i.e. would break if
KVM extends KVM_SYNC_X86_VALID_FIELDS.  (c) KVM_SYNC_X86_VALID_FIELDS probably
shouldn't be defined in a uapi header; for all intents and purposes it's a KVM-
internal details.

>  #define INVALID_SYNC_FIELD 0x80000000
>  
>  /*
> @@ -255,7 +255,6 @@ KVM_ONE_VCPU_TEST(sync_regs_test, req_and_verify_all_valid, guest_code)
>  	struct kvm_regs regs;
>  
>  	/* Request and verify all valid register sets. */
> -	/* TODO: BUILD TIME CHECK: TEST_ASSERT(KVM_SYNC_X86_NUM_FIELDS != 3); */
>  	run->kvm_valid_regs = TEST_SYNC_FIELDS;
>  	vcpu_run(vcpu);
>  	TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO);
> -- 
> 2.54.0
>