Re: [RESEND PATCH] kvm/selftests: Close opened file descriptor in stable_tsc_check_supported()

[Sean Christopherson <seanjc@xxxxxxxxxx>]

On Wed, Apr 05, 2023, Hao Ge wrote:
> Close the "current_clocksource" file descriptor before
> returning or exiting from stable_tsc_check_supported()
> in vmx_nested_tsc_scaling_test
> 
> Signed-off-by: Hao Ge <gehao@xxxxxxxxxx>
> ---
>  .../selftests/kvm/x86_64/vmx_nested_tsc_scaling_test.c    | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/x86_64/vmx_nested_tsc_scaling_test.c b/tools/testing/selftests/kvm/x86_64/vmx_nested_tsc_scaling_test.c
> index d427eb146bc5..fa03c8d1ce4e 100644
> --- a/tools/testing/selftests/kvm/x86_64/vmx_nested_tsc_scaling_test.c
> +++ b/tools/testing/selftests/kvm/x86_64/vmx_nested_tsc_scaling_test.c
> @@ -126,12 +126,16 @@ static void stable_tsc_check_supported(void)
>  		goto skip_test;
>  
>  	if (fgets(buf, sizeof(buf), fp) == NULL)
> -		goto skip_test;
> +		goto close_fp;
>  
>  	if (strncmp(buf, "tsc", sizeof(buf)))
> -		goto skip_test;
> +		goto close_fp;
>  
> +	fclose(fp);
>  	return;
> +
> +close_fp:
> +	fclose(fp);
>  skip_test:
>  	print_skip("Kernel does not use TSC clocksource - assuming that host TSC is not stable");
>  	exit(KSFT_SKIP);

Actually, this can be streamlined by having the helper return a bool and punting
the skip logic to TEST_REQUIRE.  I'll still apply this patch first, but I'll post
a patch on top to yield:

static bool system_has_stable_tsc(void)
{
	bool tsc_is_stable;
	FILE *fp;
	char buf[4];

	fp = fopen("/sys/devices/system/clocksource/clocksource0/current_clocksource", "r");
	if (fp == NULL)
		return false;

	tsc_is_stable = fgets(buf, sizeof(buf), fp) &&
			!strncmp(buf, "tsc", sizeof(buf));

	fclose(fp);
	return tsc_is_stable;
}