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

[Alex Williamson <alex.williamson@redhat.com>]

On Thu, 18 May 2023 12:31:07 +0000
"Liu, Yi L" <yi.l.liu@intel.com> wrote:

> > 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?

This patch is fine so long as it's noted in the commit log.  Thanks,

Alex
 
> > >  }
> > >
> > >  /*
> > > 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,  
>