linux-kernel - Re: [PATCH] KVM: selftests: Fix MWAIT error message when guest assertion fails

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Date:   Sun, 19 Nov 2023 19:38:06 +0200
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: selftests: Fix MWAIT error message when guest
 assertion fails

On Tue, 2023-11-07 at 10:21 -0800, Sean Christopherson wrote:
> Print out the test and vector as intended when a guest assert fails an
> assertion regarding MONITOR/MWAIT faulting.  Unfortunately, the guest
> printf support doesn't detect such issues at compile-time, so the bug
> manifests as a confusing error message, e.g. in the most confusing case,
> the test complains that it got vector "0" instead of expected vector "0".
> 
> Fixes: 0f52e4aaa614 ("KVM: selftests: Convert the MONITOR/MWAIT test to use printf guest asserts")
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c b/tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c
> index 80aa3d8b18f8..853802641e1e 100644
> --- a/tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c
> +++ b/tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c
> @@ -27,10 +27,12 @@ do {									\
>  									\
>  	if (fault_wanted)						\
>  		__GUEST_ASSERT((vector) == UD_VECTOR,			\
> -			       "Expected #UD on " insn " for testcase '0x%x', got '0x%x'", vector); \
> +			       "Expected #UD on " insn " for testcase '0x%x', got '0x%x'", \
> +			       testcase, vector);			\
>  	else								\
>  		__GUEST_ASSERT(!(vector),				\
> -			       "Expected success on " insn " for testcase '0x%x', got '0x%x'", vector); \
> +			       "Expected success on " insn " for testcase '0x%x', got '0x%x'", \
> +			       testcase, vector);			\
>  } while (0)
>  
>  static void guest_monitor_wait(int testcase)
> 
> base-commit: 45b890f7689eb0aba454fc5831d2d79763781677

I think that these days the gcc (and llvm likely) support printf annotations,
and usually complain, we should look at adding these to have a warning in such cases.

Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>

Best regards,
	Maxim Levitsky