Re: [PATCH v1] KVM: s390: selftests: CMMA: don't run if CMMA not supported

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

On Tue,  6 Jun 2023 17:05:10 +0200
Nico Boehr <nrb@linux.ibm.com> wrote:

> The test at hand queried whether the kernel supports CMMA, but in
> addition machine support is required.
> 
> Add a check whether the machine supports CMMA.
> 
> This fixes the test under G3 (z/VM, KVM).
> 
> Signed-off-by: Nico Boehr <nrb@linux.ibm.com>

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

> ---
>  tools/testing/selftests/kvm/s390x/cmma_test.c | 20 +++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/tools/testing/selftests/kvm/s390x/cmma_test.c b/tools/testing/selftests/kvm/s390x/cmma_test.c
> index 6d0751ea224b..1d73e78e8fa7 100644
> --- a/tools/testing/selftests/kvm/s390x/cmma_test.c
> +++ b/tools/testing/selftests/kvm/s390x/cmma_test.c
> @@ -660,12 +660,32 @@ struct testdef {
>  	{ "GET_CMMA_BITS: holes are skipped", test_get_skip_holes },
>  };
>  
> +/**
> + * The kernel may support CMMA, but the machine may not (i.e. if running as
> + * guest-3).
> + *
> + * In this case, the CMMA capabilities are all there, but the CMMA-related
> + * ioctls fail. To find out whether the machine supports CMMA, create a
> + * temporary VM and then query the CMMA feature of the VM.
> + */
> +static int machine_has_cmma(void)
> +{
> +	struct kvm_vm *vm = create_vm();
> +	int r;
> +
> +	r = !__kvm_has_device_attr(vm->fd, KVM_S390_VM_MEM_CTRL, KVM_S390_VM_MEM_ENABLE_CMMA);
> +	kvm_vm_free(vm);
> +
> +	return r;
> +}
> +
>  int main(int argc, char *argv[])
>  {
>  	int idx;
>  
>  	TEST_REQUIRE(kvm_has_cap(KVM_CAP_SYNC_REGS));
>  	TEST_REQUIRE(kvm_has_cap(KVM_CAP_S390_CMMA_MIGRATION));
> +	TEST_REQUIRE(machine_has_cmma());
>  
>  	ksft_print_header();
>