Date:	Tue, 23 Sep 2014 21:02:18 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Eric Northup <digitaleric@...gle.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Amit Shah <amit.shah@...hat.com>, stable@...r.kernel.org,
	lf-virt <virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH RFC] virtio_pci: fix virtio spec compliance on restore

On Tue, Sep 23, 2014 at 09:06:03AM -0700, Eric Northup wrote:
> On Tue, Sep 23, 2014 at 3:32 AM, Michael S. Tsirkin <mst@...hat.com> wrote:
> > On restore, virtio pci does the following:
> > + set features
> > + init vqs etc - device can be used at this point!
> > + set ACKNOWLEDGE,DRIVER and DRIVER_OK status bits
> >
> > This is in violation of the virtio spec, which
> > requires the following order:
> > - ACKNOWLEDGE
> > - DRIVER
> > - init vqs
> > - DRIVER_OK
> >
> > Cc: stable@...r.kernel.org
> > Cc: Amit Shah <amit.shah@...hat.com>
> > Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> > ---
> >
> > Lightly tested.
> > Will repost as non-RFC once testing is done, sending
> > out now for early flames/comments.
> >
> > Thanks!
> >
> >  drivers/virtio/virtio_pci.c | 36 ++++++++++++++++++++++++++++++++----
> >  1 file changed, 32 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/virtio/virtio_pci.c b/drivers/virtio/virtio_pci.c
> > index 58f7e45..58cbf6e 100644
> > --- a/drivers/virtio/virtio_pci.c
> > +++ b/drivers/virtio/virtio_pci.c
> > @@ -785,6 +785,7 @@ static int virtio_pci_restore(struct device *dev)
> >         struct pci_dev *pci_dev = to_pci_dev(dev);
> >         struct virtio_pci_device *vp_dev = pci_get_drvdata(pci_dev);
> >         struct virtio_driver *drv;
> > +       unsigned status = 0;
> >         int ret;
> >
> >         drv = container_of(vp_dev->vdev.dev.driver,
> > @@ -795,14 +796,41 @@ static int virtio_pci_restore(struct device *dev)
> >                 return ret;
> >
> >         pci_set_master(pci_dev);
> > +       /* We always start by resetting the device, in case a previous
> > +        * driver messed it up. */
> > +       vp_reset(&vp_dev->vdev);
> 
> This should happen before enabling PCI bus mastering.

this is the order of events in initialization,
it seems better to be consistent.

> > +
> > +       /* Acknowledge that we've seen the device. */
> > +       status |= VIRTIO_CONFIG_S_ACKNOWLEDGE;
> > +       vp_set_status(&vp_dev->vdev, status);
> > +
> > +       /* Maybe driver failed before freeze.
> > +        * Restore the failed status, for debugging. */
> > +       status |= vp_dev->saved_status & VIRTIO_CONFIG_S_FAILED;
> > +       vp_set_status(&vp_dev->vdev, status);
> > +
> > +       if (!drv)
> > +               return 0;
> > +
> > +       /* We have a driver! */
> > +       status |= VIRTIO_CONFIG_S_DRIVER;
> > +       vp_set_status(&vp_dev->vdev, status);
> > +
> >         vp_finalize_features(&vp_dev->vdev);
> >
> > -       if (drv && drv->restore)
> > -               ret = drv->restore(&vp_dev->vdev);
> > +       if (!drv->restore)
> > +               return 0;
> > +
> > +       ret = drv->restore(&vp_dev->vdev);
> > +       if (ret) {
> > +               status |= VIRTIO_CONFIG_S_FAILED;
> > +               vp_set_status(&vp_dev->vdev, status);
> > +               return ret;
> > +       }
> >
> >         /* Finally, tell the device we're all set */
> > -       if (!ret)
> > -               vp_set_status(&vp_dev->vdev, vp_dev->saved_status);
> > +       status |= VIRTIO_CONFIG_S_DRIVER_OK;
> > +       vp_set_status(&vp_dev->vdev, status);
> >
> >         return ret;
> >  }
> > --
> > MST
> > _______________________________________________
> > Virtualization mailing list
> > Virtualization@...ts.linux-foundation.org
> > https://lists.linuxfoundation.org/mailman/listinfo/virtualization
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