RE: [PATCH v5 07/10] vfio: Add helper to search vfio_device in a dev_set

Liu, Yi L
2023-05-18T12:31:22Z

> From: Alex Williamson <alex.williamson@redhat.com>
> Sent: Thursday, May 18, 2023 3:13 AM
>
> On Sat, 13 May 2023 06:21:33 -0700
> Yi Liu <yi.l.liu@intel.com> wrote:
>
> > There are drivers that need to search vfio_device within a given dev_set.
> > e.g. vfio-pci. So add a helper.
> >
> > Signed-off-by: Yi Liu <yi.l.liu@intel.com>
> > ---
> > drivers/vfio/pci/vfio_pci_core.c | 8 +++-----
> > drivers/vfio/vfio_main.c | 15 +++++++++++++++
> > include/linux/vfio.h | 3 +++
> > 3 files changed, 21 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
> > index 39e7823088e7..4df2def35bdd 100644
> > --- a/drivers/vfio/pci/vfio_pci_core.c
> > +++ b/drivers/vfio/pci/vfio_pci_core.c
> > @@ -2335,12 +2335,10 @@ static bool vfio_dev_in_groups(struct
> vfio_pci_core_device *vdev,
> > static int vfio_pci_is_device_in_set(struct pci_dev *pdev, void *data)
> > {
> > struct vfio_device_set *dev_set = data;
> > - struct vfio_device *cur;
> >
> > - list_for_each_entry(cur, &dev_set->device_list, dev_set_list)
> > - if (cur->dev == &pdev->dev)
> > - return 0;
> > - return -EBUSY;
> > + lockdep_assert_held(&dev_set->lock);
> > +
> > + return vfio_find_device_in_devset(dev_set, &pdev->dev) ? 0 : -EBUSY;
>
> Maybe an opportunity to revisit why this returns -EBUSY rather than
> something reasonable like -ENODEV. It looks like we picked up the
> -EBUSY in a882c16a2b7e where I think it was trying to preserve the
> return of vfio_pci_try_zap_and_vma_lock_cb() but the return value here
> is not even propagated so this looks like an chance to have it make
> sense again. Thanks,

From the name of this function, yes, -ENODEV is better. is it
Ok to modify it to be -ENODEV in this patch or a separate one?

Regards,
Yi Liu

>
> > }
> >
> > /*
> > diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
> > index f0ca33b2e1df..ab4f3a794f78 100644
> > --- a/drivers/vfio/vfio_main.c
> > +++ b/drivers/vfio/vfio_main.c
> > @@ -141,6 +141,21 @@ unsigned int vfio_device_set_open_count(struct
> vfio_device_set *dev_set)
> > }
> > EXPORT_SYMBOL_GPL(vfio_device_set_open_count);
> >
> > +struct vfio_device *
> > +vfio_find_device_in_devset(struct vfio_device_set *dev_set,
> > + struct device *dev)
> > +{
> > + struct vfio_device *cur;
> > +
> > + lockdep_assert_held(&dev_set->lock);
> > +
> > + list_for_each_entry(cur, &dev_set->device_list, dev_set_list)
> > + if (cur->dev == dev)
> > + return cur;
> > + return NULL;
> > +}
> > +EXPORT_SYMBOL_GPL(vfio_find_device_in_devset);
> > +
> > /*
> > * Device objects - create, release, get, put, search
> > */
> > diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> > index fcbe084b18c8..4c17395ed4d2 100644
> > --- a/include/linux/vfio.h
> > +++ b/include/linux/vfio.h
> > @@ -259,6 +259,9 @@ void vfio_unregister_group_dev(struct vfio_device *device);
> >
> > int vfio_assign_device_set(struct vfio_device *device, void *set_id);
> > unsigned int vfio_device_set_open_count(struct vfio_device_set *dev_set);
> > +struct vfio_device *
> > +vfio_find_device_in_devset(struct vfio_device_set *dev_set,
> > + struct device *dev);
> >
> > int vfio_mig_get_next_state(struct vfio_device *device,
> > enum vfio_device_mig_state cur_fsm,