Re: [PATCH v3 2/4] tests/qtest/migration: Add infrastructure to skip tests on older QEMUs

[Peter Xu <peterx@redhat.com>]

On Fri, Jan 05, 2024 at 03:04:47PM -0300, Fabiano Rosas wrote:
> We can run the migration tests with two different QEMU binaries to
> test migration compatibility between QEMU versions. This means we'll
> be running the tests with an older QEMU in either source or
> destination.
> 
> We need to avoid trying to test functionality that is unknown to the
> older QEMU. This could mean new features, bug fixes, error message
> changes, QEMU command line changes, migration API changes, etc.
> 
> Add a 'since' argument to the tests that inform when the functionality
> that is being test has been added to QEMU so we can skip the test on
> older versions.
> 
> Also add a version comparison function so we can adapt test code
> depending on the QEMU binary version being used.
> 
> Signed-off-by: Fabiano Rosas <farosas@suse.de>
> ---
>  tests/qtest/migration-helpers.h |  1 +
>  tests/qtest/migration-helpers.c | 48 +++++++++++++++++++++++++++++++++
>  tests/qtest/migration-test.c    | 29 ++++++++++++++++++++
>  3 files changed, 78 insertions(+)
> 
> diff --git a/tests/qtest/migration-helpers.h b/tests/qtest/migration-helpers.h
> index e31dc85cc7..7b4f8e851e 100644
> --- a/tests/qtest/migration-helpers.h
> +++ b/tests/qtest/migration-helpers.h
> @@ -47,4 +47,5 @@ char *find_common_machine_version(const char *mtype, const char *var1,
>                                    const char *var2);
>  char *resolve_machine_version(const char *alias, const char *var1,
>                                const char *var2);
> +int migration_vercmp(QTestState *who, const char *tgt_version);
>  #endif /* MIGRATION_HELPERS_H */
> diff --git a/tests/qtest/migration-helpers.c b/tests/qtest/migration-helpers.c
> index 24fb7b3525..bc4fd93e8c 100644
> --- a/tests/qtest/migration-helpers.c
> +++ b/tests/qtest/migration-helpers.c
> @@ -292,3 +292,51 @@ char *resolve_machine_version(const char *alias, const char *var1,
>  
>      return find_common_machine_version(machine_name, var1, var2);
>  }
> +
> +int migration_vercmp(QTestState *who, const char *tgt_version)
> +{
> +    g_autofree char *version = g_strdup(tgt_version);
> +    int major = 0, minor = 0, micro = 0;
> +    int tgt_major = 0, tgt_minor = 0, tgt_micro = 0;
> +    const char *delim = ".";
> +    char *tok;
> +
> +    qtest_query_version(who, &major, &minor, &micro);
> +
> +    tok = strtok(version, delim);
> +    assert(tok);
> +    tgt_major = atoi(tok);
> +    assert(tgt_major);

I'd consider dropping this.  But I don't think "since: 0.8" is valid. :)
More like a nitpick.

> +
> +    if (major > tgt_major) {
> +        return -1;

This means the QEMU version is newer, the function will return negative.
Is this what we want?  It seems it's inverted.

In all cases, document this function with retval would be helpful too.

> +    }
> +    if (major < tgt_major) {
> +        return 1;
> +    }

Instead of all these, I'm wondering whether we can allow "since" to be an
array of integers, like [8, 2, 0].  Would that be much easier?

> +
> +    tok = strtok(NULL, delim);
> +    assert(tok);
> +    tgt_minor = atoi(tok);
> +
> +    if (minor > tgt_minor) {
> +        return -1;
> +    }
> +    if (minor < tgt_minor) {
> +        return 1;
> +    }
> +
> +    tok = strtok(NULL, delim);
> +    if (tok) {
> +        tgt_micro = atoi(tok);
> +    }
> +
> +    if (micro > tgt_micro) {
> +        return -1;
> +    }
> +    if (micro < tgt_micro) {
> +        return 1;
> +    }
> +
> +    return 0;
> +}
> diff --git a/tests/qtest/migration-test.c b/tests/qtest/migration-test.c
> index d520c587f7..001470238b 100644
> --- a/tests/qtest/migration-test.c
> +++ b/tests/qtest/migration-test.c
> @@ -637,6 +637,12 @@ typedef struct {
>      bool use_dirty_ring;
>      const char *opts_source;
>      const char *opts_target;
> +    /*
> +     * If a test checks against new functionality that might not be
> +     * present in older QEMUs this needs to be set so we can skip
> +     * running it when doing compatibility testing.
> +     */
> +    const char *since;
>  } MigrateStart;
>  
>  /*
> @@ -850,6 +856,17 @@ static int test_migrate_start(QTestState **from, QTestState **to,
>          qtest_qmp_set_event_callback(*from,
>                                       migrate_watch_for_stop,
>                                       &got_src_stop);
> +
> +        if (args->since && migration_vercmp(*from, args->since) < 0) {
> +            g_autofree char *msg = NULL;
> +
> +            msg = g_strdup_printf("Test requires at least QEMU version %s",
> +                                  args->since);
> +            g_test_skip(msg);
> +            qtest_quit(*from);
> +
> +            return -1;
> +        }
>      }
>  
>      cmd_target = g_strdup_printf("-accel kvm%s -accel tcg "
> @@ -872,6 +889,18 @@ static int test_migrate_start(QTestState **from, QTestState **to,
>                                   migrate_watch_for_resume,
>                                   &got_dst_resume);
>  
> +    if (args->since && migration_vercmp(*to, args->since) < 0) {
> +        g_autofree char *msg = NULL;
> +
> +        msg = g_strdup_printf("Test requires at least QEMU version %s",
> +                              args->since);
> +        g_test_skip(msg);
> +        qtest_quit(*to);
> +        qtest_quit(*from);
> +
> +        return -1;

Nitpick: you can do both check here, then avoid duplicating some code, and
always free from+to.

> +    }
> +
>      /*
>       * Remove shmem file immediately to avoid memory leak in test failed case.
>       * It's valid because QEMU has already opened this file
> -- 
> 2.35.3
> 

-- 
Peter Xu