Re: [PATCH 2/2] KVM: selftests: Fail tests when open() fails with !ENOENT

[Sean Christopherson <seanjc@google.com>]

On Wed, Jan 24, 2024, Vitaly Kuznetsov wrote:
> open_path_or_exit() is used for '/dev/kvm', '/dev/sev', and
> '/sys/module/%s/parameters/%s' and skipping test when the entry is missing
> is completely reasonable. Other errors, however, may indicate a real issue
> which is easy to miss. E.g. when 'hyperv_features' test was entering an
> infinite loop the output was:
> 
> ./hyperv_features
> Testing access to Hyper-V specific MSRs
> 1..0 # SKIP - /dev/kvm not available (errno: 24)
> 
> and this can easily get overlooked.
> 
> Keep ENOENT case 'special' for skipping tests and fail when open() results
> in any other errno.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
>  tools/testing/selftests/kvm/lib/kvm_util.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index e066d584c656..f3dfd0d38b7f 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -27,7 +27,8 @@ int open_path_or_exit(const char *path, int flags)
>  	int fd;
>  
>  	fd = open(path, flags);
> -	__TEST_REQUIRE(fd >= 0, "%s not available (errno: %d)", path, errno);
> +	__TEST_REQUIRE(fd >= 0 || errno != ENOENT, "%s not present", path);

Rather than make up our own error messages, can we use strerror()?

> +	TEST_ASSERT(fd >= 0, "%s not available (errno: %d)", path, errno);

And then here just say "Failed to open '%s'" and let test_assert() fill in the
strerror() information.