Re: [kvm-unit-tests PATCH v1 1/4] lib: add function to request migration

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

On Wed, 30 Nov 2022 15:22:46 +0100
Nico Boehr <nrb@linux.ibm.com> wrote:

> Migration tests can ask migrate_cmd to migrate them to a new QEMU
> process. Requesting migration and waiting for completion is hence a
> common pattern which is repeated all over the code base. Add a function
> which does all of that to avoid repeating the same pattern.
> 
> Since migrate_cmd currently can only migrate exactly once, this function
> is called migrate_once() and is a no-op when it has been called before.
> This can simplify the control flow, especially when tests are skipped.
> 
> Suggested-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> Signed-off-by: Nico Boehr <nrb@linux.ibm.com>

I like the code, I only have one concern

> ---
>  lib/migrate.c | 34 ++++++++++++++++++++++++++++++++++
>  lib/migrate.h |  9 +++++++++
>  2 files changed, 43 insertions(+)
>  create mode 100644 lib/migrate.c
>  create mode 100644 lib/migrate.h
> 
> diff --git a/lib/migrate.c b/lib/migrate.c
> new file mode 100644
> index 000000000000..50e78fb08865
> --- /dev/null
> +++ b/lib/migrate.c
> @@ -0,0 +1,34 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Migration-related functions
> + *
> + * Copyright IBM Corp. 2022
> + * Author: Nico Boehr <nrb@linux.ibm.com>
> + */
> +#include <libcflat.h>
> +#include "migrate.h"
> +
> +/* static for now since we only support migrating exactly once per test. */
> +static void migrate(void)
> +{
> +	puts("Please migrate me, then press return\n");

the other architectures use a slightly different message, maybe we
should use that also on s390x?

In the end it _should_ not matter, since the migrate_cmd looks for one
specific keyword, but I still think we should try to minimize the
impact of this series. And I know that changing the migration message
will not break anything on s390x.

> +	(void)getchar();
> +	report_info("Migration complete");
> +}
> +
> +/*
> + * Initiate migration and wait for it to complete.
> + * If this function is called more than once, it is a no-op.
> + * Since migrate_cmd can only migrate exactly once this function can
> + * simplify the control flow, especially when skipping tests.
> + */
> +void migrate_once(void)
> +{
> +	static bool migrated;
> +
> +	if (migrated)
> +		return;
> +
> +	migrated = true;
> +	migrate();
> +}
> diff --git a/lib/migrate.h b/lib/migrate.h
> new file mode 100644
> index 000000000000..3c94e6af761c
> --- /dev/null
> +++ b/lib/migrate.h
> @@ -0,0 +1,9 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Migration-related functions
> + *
> + * Copyright IBM Corp. 2022
> + * Author: Nico Boehr <nrb@linux.ibm.com>
> + */
> +
> +void migrate_once(void);