Re: [PATCH RFC 3/3] vhost, kcov: collect coverage from vhost_worker

[Andrey Konovalov]

On Thu, Oct 17, 2019 at 8:18 PM Greg Kroah-Hartman
<gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Thu, Oct 17, 2019 at 07:44:15PM +0200, Andrey Konovalov wrote:
> > This patch adds kcov_remote_start/kcov_remote_stop annotations to the
> > vhost_worker function, which is responsible for processing vhost works.
> > Since vhost_worker is spawned when a vhost device instance is created,
> > the common kcov handle is used for kcov_remote_start/stop annotations.
> >
> > Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
> > ---
> >  drivers/vhost/vhost.c | 15 +++++++++++++++
> >  drivers/vhost/vhost.h |  3 +++
> >  2 files changed, 18 insertions(+)
> >
> > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> > index 36ca2cf419bf..71a349f6b352 100644
> > --- a/drivers/vhost/vhost.c
> > +++ b/drivers/vhost/vhost.c
> > @@ -357,7 +357,13 @@ static int vhost_worker(void *data)
> >               llist_for_each_entry_safe(work, work_next, node, node) {
> >                       clear_bit(VHOST_WORK_QUEUED, &work->flags);
> >                       __set_current_state(TASK_RUNNING);
> > +#ifdef CONFIG_KCOV
> > +                     kcov_remote_start(dev->kcov_handle);
> > +#endif
>
> Shouldn't you hide these #ifdefs in a .h file?  This is not a "normal"
> kernel coding style at all.

Well, if it's acceptable to add a kcov_handle field into vhost_dev
even when CONFIG_KCOV is not enabled, then we can get rid of those
#ifdefs.

>
> >                       work->fn(work);
> > +#ifdef CONFIG_KCOV
> > +                     kcov_remote_stop();
> > +#endif
> >                       if (need_resched())
> >                               schedule();
> >               }
> > @@ -546,6 +552,9 @@ long vhost_dev_set_owner(struct vhost_dev *dev)
> >
> >       /* No owner, become one */
> >       dev->mm = get_task_mm(current);
> > +#ifdef CONFIG_KCOV
> > +     dev->kcov_handle = current->kcov_handle;
> > +#endif
> >       worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);
> >       if (IS_ERR(worker)) {
> >               err = PTR_ERR(worker);
> > @@ -571,6 +580,9 @@ long vhost_dev_set_owner(struct vhost_dev *dev)
> >       if (dev->mm)
> >               mmput(dev->mm);
> >       dev->mm = NULL;
> > +#ifdef CONFIG_KCOV
> > +     dev->kcov_handle = 0;
> > +#endif
> >  err_mm:
> >       return err;
> >  }
> > @@ -682,6 +694,9 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
> >       if (dev->worker) {
> >               kthread_stop(dev->worker);
> >               dev->worker = NULL;
> > +#ifdef CONFIG_KCOV
> > +             dev->kcov_handle = 0;
> > +#endif
> >       }
> >       if (dev->mm)
> >               mmput(dev->mm);
> > diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> > index e9ed2722b633..010ca1ebcbd5 100644
> > --- a/drivers/vhost/vhost.h
> > +++ b/drivers/vhost/vhost.h
> > @@ -173,6 +173,9 @@ struct vhost_dev {
> >       int iov_limit;
> >       int weight;
> >       int byte_weight;
> > +#ifdef CONFIG_KCOV
> > +     u64 kcov_handle;
> > +#endif
>
> Why is this a #ifdef at all here?
>
> thanks,
>
> greg k-h