> From: Jason Gunthorpe <jgg@xxxxxxxxxx> > Sent: Wednesday, September 22, 2021 8:40 PM > > On Wed, Sep 22, 2021 at 01:47:05AM +0000, Tian, Kevin wrote: > > > > IIRC in VFIO the container is the IOAS and when the group goes to > > > create the device fd it should simply do the > > > iommu_device_init_user_dma() followed immediately by a call to bind > > > the container IOAS as your #3. > > > > a slight correction. > > > > to meet vfio semantics we could do init_user_dma() at group attach > > time and then call binding to container IOAS when the device fd > > is created. This is because vfio requires the group in a security context > > before the device is opened. > > Is it? Until a device FD is opened the group fd is kind of idle, right? yes, then there is no user-tangible difference between init_user_dma() at group attach time vs. doing it when opening fd(). But the latter does require more change than the former, as it also needs the vfio iommu driver to provide a .device_attach callback. What's in my mind now is to keep existing group attach sequence which further calls a group-version init_user_dma(). Then when device fd is created, just create a iommu_dev object and switch to normal fops. > > > > Ie the basic flow would see the driver core doing some: > > > > Just double confirm. Is there concern on having the driver core to > > call iommu functions? > > It is always an interesting question, but I'd say iommu is > foundantional to Linux and if it needs driver core help it shouldn't > be any different from PM, pinctl, or other subsystems that have > inserted themselves into the driver core. > > Something kind of like the below. > > If I recall, once it is done like this then the entire iommu notifier > infrastructure can be ripped out which is a lot of code. thanks for the guidance. will think more along this direction... > > > diff --git a/drivers/base/dd.c b/drivers/base/dd.c > index 68ea1f949daa90..e39612c99c6123 100644 > --- a/drivers/base/dd.c > +++ b/drivers/base/dd.c > @@ -566,6 +566,10 @@ static int really_probe(struct device *dev, struct > device_driver *drv) > goto done; > } > > + ret = iommu_set_kernel_ownership(dev); > + if (ret) > + return ret; > + > re_probe: > dev->driver = drv; > > @@ -673,6 +677,7 @@ static int really_probe(struct device *dev, struct > device_driver *drv) > dev->pm_domain->dismiss(dev); > pm_runtime_reinit(dev); > dev_pm_set_driver_flags(dev, 0); > + iommu_release_kernel_ownership(dev); > done: > return ret; > } > @@ -1214,6 +1219,7 @@ static void __device_release_driver(struct device > *dev, struct device *parent) > dev->pm_domain->dismiss(dev); > pm_runtime_reinit(dev); > dev_pm_set_driver_flags(dev, 0); > + iommu_release_kernel_ownership(dev); > > klist_remove(&dev->p->knode_driver); > device_pm_check_callbacks(dev);
