linux-kernel - Re: [PATCH v3 02/14] x86/vmx: Skip vmx_pf_exception_test

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Message-ID: <aRZ6bM_yVo9-zyDT@google.com>
Date: Thu, 13 Nov 2025 16:40:12 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Yosry Ahmed <yosry.ahmed@...ux.dev>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Kevin Cheng <chengkev@...gle.com>, kvm@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 02/14] x86/vmx: Skip vmx_pf_exception_test_fep early if
 FEP is not available

On Mon, Nov 10, 2025, Yosry Ahmed wrote:
> The check to skip the test is currently performed in the guest code.
> There a few TEST_ASSERTs that happen before the guest is run, which
> internally call report_passed(). The latter increases the number of
> passed tests.
> 
> Hence, when vmx_pf_exception_test_fep is run, report_summary() does not
> return a "skip" error code because the total number of tests is larger
> than the number of skipped tests.
> 
> Skip early if FEP is not available, before any assertions, such that
> report_summary() finds exactly 1 skipped test and returns the
> appropriate error code.
> 
> Signed-off-by: Yosry Ahmed <yosry.ahmed@...ux.dev>
> ---
>  x86/vmx_tests.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/x86/vmx_tests.c b/x86/vmx_tests.c
> index 0b3cfe50c6142..4f214ebdbe1d9 100644
> --- a/x86/vmx_tests.c
> +++ b/x86/vmx_tests.c
> @@ -10644,7 +10644,10 @@ static void vmx_pf_exception_test(void)
>  
>  static void vmx_pf_exception_forced_emulation_test(void)
>  {
> -	__vmx_pf_exception_test(NULL, NULL, vmx_pf_exception_forced_emulation_test_guest);
> +	if (is_fep_available)
> +		__vmx_pf_exception_test(NULL, NULL, vmx_pf_exception_forced_emulation_test_guest);
> +	else
> +		report_skip("Forced emulation prefix (FEP) not available\n");

To be consistent with other tests, and the kernel's general pattern of:

	if (<error>) {
		<react>
		return;
	}

	<do useful stuff>

I'll tweak this to

	if (!is_fep_available) {
		report_skip("Forced emulation prefix (FEP) not available\n");
		return;
	}

	__vmx_pf_exception_test(NULL, NULL, vmx_pf_exception_forced_emulation_test_guest);

when applying.