> -----Original Message----- > From: Alex Williamson <alex.williamson@xxxxxxxxxx> > Sent: Friday, March 8, 2019 4:33 PM > To: Parav Pandit <parav@xxxxxxxxxxxx> > Cc: netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > michal.lkml@xxxxxxxxxxx; davem@xxxxxxxxxxxxx; > gregkh@xxxxxxxxxxxxxxxxxxx; Jiri Pirko <jiri@xxxxxxxxxxxx>; > kwankhede@xxxxxxxxxx; Vu Pham <vuhuong@xxxxxxxxxxxx>; Yuval Avnery > <yuvalav@xxxxxxxxxxxx>; jakub.kicinski@xxxxxxxxxxxxx; > kvm@xxxxxxxxxxxxxxx > Subject: Re: [RFC net-next v1 1/3] vfio/mdev: Inherit dma masks of parent > device > > On Fri, 8 Mar 2019 16:07:54 -0600 > Parav Pandit <parav@xxxxxxxxxxxx> wrote: > > > Inherit dma mask of parent device in child mdev devices, so that > > protocol stack can use right dma mask while doing dma mappings. > > > > Signed-off-by: Parav Pandit <parav@xxxxxxxxxxxx> > > --- > > drivers/vfio/mdev/mdev_core.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/drivers/vfio/mdev/mdev_core.c > > b/drivers/vfio/mdev/mdev_core.c index 0212f0e..9b8bdc9 100644 > > --- a/drivers/vfio/mdev/mdev_core.c > > +++ b/drivers/vfio/mdev/mdev_core.c > > @@ -315,6 +315,10 @@ int mdev_device_create(struct kobject *kobj, > struct device *dev, uuid_le uuid) > > mdev->dev.parent = dev; > > mdev->dev.bus = &mdev_bus_type; > > mdev->dev.release = mdev_device_release; > > + mdev->dev.dma_mask = dev->dma_mask; > > + mdev->dev.dma_parms = dev->dma_parms; > > + mdev->dev.coherent_dma_mask = dev->coherent_dma_mask; > > + > > dev_set_name(&mdev->dev, "%pUl", uuid.b); > > > > ret = device_register(&mdev->dev); > > This seems like a rather large assumption and none of the existing mdev > drivers even make use of DMA ops. So its non-harmful anyway. > Why shouldn't this be done in mdev_parent_ops.create? Thanks, > Struct device should be setup correctly before calling device_register(). That is the sane way to access device_register() API. Doing this under mdev_parent_ops.create() will do it after device_register(). If you want to make it optional, mdev_register_device() can pass a bool flag to setup dma params or not which can be applied conditionally in mdev_device_create() before device_register().
