Re: [RFC PATCH v4 1/4] vfio-ccw: Check initialized flag in cp_init()

Cornelia Huck
2021-04-14T16:30:38Z

On Tue, 13 Apr 2021 20:24:07 +0200
Eric Farman <farman@linux.ibm.com> wrote:

> We have a really nice flag in the channel_program struct that
> indicates if it had been initialized by cp_init(), and use it
> as a guard in the other cp accessor routines, but not for a
> duplicate call into cp_init(). The possibility of this occurring
> is low, because that flow is protected by the private->io_mutex
> and FSM CP_PROCESSING state. But then why bother checking it
> in (for example) cp_prefetch() then?
>
> Let's just be consistent and check for that in cp_init() too.
>
> Fixes: 71189f263f8a3 ("vfio-ccw: make it safe to access channel programs")
> Signed-off-by: Eric Farman <farman@linux.ibm.com>
> ---
> drivers/s390/cio/vfio_ccw_cp.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
> index b9febc581b1f..8d1b2771c1aa 100644
> --- a/drivers/s390/cio/vfio_ccw_cp.c
> +++ b/drivers/s390/cio/vfio_ccw_cp.c
> @@ -638,6 +638,10 @@ int cp_init(struct channel_program *cp, struct device *mdev, union orb *orb)
> static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 1);
> int ret;
>
> + /* this is an error in the caller */
> + if (cp->initialized)
> + return -EBUSY;
> +
> /*
> * We only support prefetching the channel program. We assume all channel
> * programs executed by supported guests likewise support prefetching.

Reviewed-by: Cornelia Huck <cohuck@redhat.com>