On (Mon) 21 Jul 2014 [08:11:16], Jason Cooper wrote:
> On Mon, Jul 21, 2014 at 05:15:51PM +0530, Amit Shah wrote:
> > Instead of calling hwrng_register() in the probe routing, call it in the
> > scan routine. This ensures that when hwrng_register() is successful,
> > and it requests a few random bytes to seed the kernel's pool at init,
> > we're ready to service that request.
> >
> > This will also enable us to remove the workaround added previously to
> > check whether probe was completed, and only then ask for data from the
> > host. The revert follows in the next commit.
> >
> > There's a slight behaviour change here on unsuccessful hwrng_register().
> > Previously, when hwrng_unregister() failed, the probe() routine would
> > fail, and the vqs would be torn down, and driver would be marked not
> > initialized. Now, the vqs will remain initialized, driver would be
> > marked initialized as well, but won't be available in the list of RNGs
> > available to hwrng core. To fix the failures, the procedure remains the
> > same, i.e. unload and re-load the module, and hope things succeed the
> > next time around.
>
> I'm not too comfortable with this. I'll try to take a closer look
> tonight, but in the meantime...
>
> > Signed-off-by: Amit Shah <[email protected]>
> > ---
> > drivers/char/hw_random/virtio-rng.c | 25 +++++++++++++++----------
> > 1 file changed, 15 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/char/hw_random/virtio-rng.c
> > b/drivers/char/hw_random/virtio-rng.c
> > index a156284..d9927eb 100644
> > --- a/drivers/char/hw_random/virtio-rng.c
> > +++ b/drivers/char/hw_random/virtio-rng.c
> > @@ -35,6 +35,7 @@ struct virtrng_info {
> > unsigned int data_avail;
> > int index;
> > bool busy;
> > + bool hwrng_register_done;
> > };
> >
> > static bool probe_done;
> > @@ -136,15 +137,6 @@ static int probe_common(struct virtio_device *vdev)
> > return err;
> > }
> >
> > - err = hwrng_register(&vi->hwrng);
> > - if (err) {
> > - vdev->config->del_vqs(vdev);
> > - vi->vq = NULL;
> > - kfree(vi);
> > - ida_simple_remove(&rng_index_ida, index);
> > - return err;
> > - }
> > -
>
> This needs to stay. register, and failure to do so, should occur in the
> probe routine.
Can you elaborate why?
> > probe_done = true;
> > return 0;
> > }
> > @@ -152,9 +144,11 @@ static int probe_common(struct virtio_device *vdev)
> > static void remove_common(struct virtio_device *vdev)
> > {
> > struct virtrng_info *vi = vdev->priv;
> > +
> > vdev->config->reset(vdev);
> > vi->busy = false;
> > - hwrng_unregister(&vi->hwrng);
> > + if (vi->hwrng_register_done)
> > + hwrng_unregister(&vi->hwrng);
> > vdev->config->del_vqs(vdev);
> > ida_simple_remove(&rng_index_ida, vi->index);
> > kfree(vi);
> > @@ -170,6 +164,16 @@ static void virtrng_remove(struct virtio_device *vdev)
> > remove_common(vdev);
> > }
> >
> > +static void virtrng_scan(struct virtio_device *vdev)
> > +{
> > + struct virtrng_info *vi = vdev->priv;
> > + int err;
> > +
> > + err = hwrng_register(&vi->hwrng);
> > + if (!err)
> > + vi->hwrng_register_done = true;
>
> Instead, perhaps we should just feed the entropy pool from here? We
> would still need to prevent the core from doing so. Perhaps back to the
> flag idea?
No way hwrng knows the difference between probe and scan for
virtio-rng, so it's back to the delayed workqueue idea, if this isn't
usable..
But I need to understand why this isn't workable.
Thanks,
Amit
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