Re: [PATCH v4 2/4] KVM: selftests: add is_cpu_eligible_to_run() utility function

[Oliver Upton <oupton@google.com>]

Hi Ricardo,

On Mon, Apr 04, 2022 at 02:46:40PM -0700, Ricardo Koller wrote:
> Add is_cpu_eligible_to_run() utility function, which checks whether the current
> process, or one of its threads, is eligible to run on a particular CPU.
> This information is obtained using sched_getaffinity.
> 
> Signed-off-by: Ricardo Koller <ricarkol@google.com>
> ---
>  .../testing/selftests/kvm/include/test_util.h |  2 ++
>  tools/testing/selftests/kvm/lib/test_util.c   | 20 ++++++++++++++++++-
>  2 files changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
> index 99e0dcdc923f..a7653f369b6c 100644
> --- a/tools/testing/selftests/kvm/include/test_util.h
> +++ b/tools/testing/selftests/kvm/include/test_util.h
> @@ -143,4 +143,6 @@ static inline void *align_ptr_up(void *x, size_t size)
>  	return (void *)align_up((unsigned long)x, size);
>  }
>  
> +bool is_cpu_eligible_to_run(int pcpu);
> +
>  #endif /* SELFTEST_KVM_TEST_UTIL_H */
> diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
> index 6d23878bbfe1..7813a68333c0 100644
> --- a/tools/testing/selftests/kvm/lib/test_util.c
> +++ b/tools/testing/selftests/kvm/lib/test_util.c
> @@ -4,6 +4,7 @@
>   *
>   * Copyright (C) 2020, Google LLC.
>   */
> +#define _GNU_SOURCE
>  
>  #include <assert.h>
>  #include <ctype.h>
> @@ -13,7 +14,9 @@
>  #include <sys/stat.h>
>  #include <sys/syscall.h>
>  #include <linux/mman.h>
> -#include "linux/kernel.h"
> +#include <linux/kernel.h>
> +#include <sched.h>
> +#include <sys/sysinfo.h>
>  
>  #include "test_util.h"
>  
> @@ -334,3 +337,18 @@ long get_run_delay(void)
>  
>  	return val[1];
>  }
> +
> +bool is_cpu_eligible_to_run(int pcpu)
> +{
> +	cpu_set_t cpuset;
> +	long i, nprocs;
> +
> +	nprocs = get_nprocs_conf();
> +	sched_getaffinity(0, sizeof(cpu_set_t), &cpuset);
> +	for (i = 0; i < nprocs; i++) {
> +		if (i == pcpu)
> +			return CPU_ISSET(i, &cpuset);
> +	}

I don't think you need the loop and can just do CPU_ISSET(pcpu, &cpuset),
right?

--
Thanks,
Oliver