Re: [RFC v2 1/3] tests: qtest: add qtest_has_kvm() to check if tested binary supports KVM

[Igor Mammedov <imammedo@redhat.com>]

On Thu, 17 Jun 2021 06:00:31 -0400
Igor Mammedov <imammedo@redhat.com> wrote:

Paolo,
Is it acceptable to (ab)use meson like in this patch?

> Currently it not possible to create tests that have KVM as a hard
> requirement on a host that doesn't support KVM for tested target
> binary (modulo going through the trouble of compiling out
> the offending test case).
> 
> Following scenario makes test fail when it's run on non x86 host:
>   qemu-system-x86_64 -enable-kvm -M q35,kernel-irqchip=on -smp 1,maxcpus=288
> 
> This patch introduces qtest_has_kvm() to let users check if KVM is
> available in advance and skip registering non run-able test-cases.
> 
> PS:
> It's simplistic and not as versatile/precise as earlier proposed
> 'query-accels' series, but it get job done for simple cases.
> 
> on upside it's much cheaper to execute than the 'query-accels' as
> it doesn't need to run QEMU for probing.
> 
> Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> ---
> v2:
>   - fix access() check.
>      s/access()/!access()/
>   - format C array items at meson.build time, and drop
>     splitting targets string at runtime
> 
>  tests/qtest/libqos/libqtest.h |  7 +++++++
>  meson.build                   |  2 ++
>  tests/qtest/libqtest.c        | 18 ++++++++++++++++++
>  3 files changed, 27 insertions(+)
> 
> diff --git a/tests/qtest/libqos/libqtest.h b/tests/qtest/libqos/libqtest.h
> index a68dcd79d4..bab0047117 100644
> --- a/tests/qtest/libqos/libqtest.h
> +++ b/tests/qtest/libqos/libqtest.h
> @@ -588,6 +588,13 @@ bool qtest_big_endian(QTestState *s);
>   */
>  const char *qtest_get_arch(void);
>  
> +/**
> + * qtest_has_kvm:
> + *
> + * Returns: True if the QEMU executable under test supports KVM
> + */
> +bool qtest_has_kvm(void);
> +
>  /**
>   * qtest_add_func:
>   * @str: Test case path.
> diff --git a/meson.build b/meson.build
> index d2a9ce91f5..7fec4e8289 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -75,6 +75,8 @@ elif cpu in ['mips', 'mips64']
>  else
>    kvm_targets = []
>  endif
> +kvm_targets_c = '"' + '" ,"'.join(kvm_targets) + '"'
> +config_host_data.set('CONFIG_KVM_TARGETS', kvm_targets_c)
>  
>  accelerator_targets = { 'CONFIG_KVM': kvm_targets }
>  if cpu in ['x86', 'x86_64', 'arm', 'aarch64']
> diff --git a/tests/qtest/libqtest.c b/tests/qtest/libqtest.c
> index 825b13a44c..daa6d54059 100644
> --- a/tests/qtest/libqtest.c
> +++ b/tests/qtest/libqtest.c
> @@ -920,6 +920,24 @@ const char *qtest_get_arch(void)
>      return end + 1;
>  }
>  
> +bool qtest_has_kvm(void)
> +{
> +    int i;
> +    bool ret = false;
> +    const char *arch = qtest_get_arch();
> +    const char *targets[] = { CONFIG_KVM_TARGETS };
> +
> +    for (i = 0; i < ARRAY_SIZE(targets); i++) {
> +        if (!strncmp(targets[i], arch, strlen(arch))) {
> +            if (!access("/dev/kvm", R_OK | W_OK)) {
> +                ret = true;
> +                break;
> +            }
> +        }
> +    }
> +    return ret;
> +}
> +
>  bool qtest_get_irq(QTestState *s, int num)
>  {
>      /* dummy operation in order to make sure irq is up to date */