[LTP] [PATCH] device-drivers/cpufreq_boost: skip test on virtual machines

[Krzysztof Kozlowski]

On 23/06/2021 10:01, Krzysztof Kozlowski wrote:
> Testing CPU frequency boost on a virtual machines is not reliable.  Even
> if cpufreq driver reports boost frequencies, the underlying hypervisor
> might decide otherwise.
> 
> For example on AWS x1e.xlarge instance (claimed to be running on Intel
> Xeon E7 8880) under Xen hypervisor the test always fails:
> 
>     cpufreq_boost    0  TINFO  :  found 'intel_pstate' driver, sysfs knob '/sys/devices/system/cpu/intel_pstate/no_turbo'
>     cpufreq_boost    0  TINFO  :  maximum speed is 3100000 KHz
>     cpufreq_boost    0  TINFO  :  load CPU0 with boost enabled
>     cpufreq_boost    0  TINFO  :  elapsed time is 1155 ms
>     cpufreq_boost    0  TINFO  :  load CPU0 with boost disabled
>     cpufreq_boost    0  TINFO  :  elapsed time is 1155 ms
>     cpufreq_boost    1  TFAIL  :  cpufreq_boost.c:186: compare time spent with and without boost (-2%)
> 
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
> ---
>  testcases/kernel/device-drivers/cpufreq/cpufreq_boost.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/testcases/kernel/device-drivers/cpufreq/cpufreq_boost.c b/testcases/kernel/device-drivers/cpufreq/cpufreq_boost.c
> index b9739db37cb7..67917b3fea25 100644
> --- a/testcases/kernel/device-drivers/cpufreq/cpufreq_boost.c
> +++ b/testcases/kernel/device-drivers/cpufreq/cpufreq_boost.c
> @@ -90,6 +90,9 @@ static void setup(void)
>  	unsigned int i;
>  	tst_require_root();
>  
> +	if (tst_is_virt(VIRT_ANY))
> +		tst_brkm(TCONF, NULL, "running in a virtual machine, overclock not reliably measureable");
> +
>  	for (i = 0; i < ARRAY_SIZE(cdrv); ++i) {
>  		fd = open(cdrv[i].file, O_RDWR);
>  		if (fd == -1)
> 

Optionally, under virtual machine the test failure could be converted to
accepted pass. This would still allow to test CPUfreq boosting
interface. Any preferences?

Best regards,
Krzysztof