On Thu, 5 May 2022 01:50:45 +0530 Kirti Wankhede <kwankhede@xxxxxxxxxx> wrote: > On 5/5/2022 12:31 AM, Jason Gunthorpe wrote: > > The last user of this function is in PCI callbacks that want to convert > > their struct pci_dev to a vfio_device. Instead of searching use the > > vfio_device available trivially through the drvdata. > > > > When a callback in the device_driver is called, the caller must hold the > > device_lock() on dev. The purpose of the device_lock is to prevent > > remove() from being called (see __device_release_driver), and allow the > > driver to safely interact with its drvdata without races. > > > > The PCI core correctly follows this and holds the device_lock() when > > calling error_detected (see report_error_detected) and > > sriov_configure (see sriov_numvfs_store). > > > > Further, since the drvdata holds a positive refcount on the vfio_device > > any access of the drvdata, under the device_lock(), from a driver callback > > needs no further protection or refcounting. > > > > Thus the remark in the vfio_device_get_from_dev() comment does not apply > > here, VFIO PCI drivers all call vfio_unregister_group_dev() from their > > remove callbacks under the device_lock() and cannot race with the > > remaining callers. > > > > Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx> > > Reviewed-by: Kirti Wankhede <kwankhede@xxxxxxxxxx> > > Reviewed-by: Shameer Kolothum <shameerali.kolothum.thodi@xxxxxxxxxx> > > Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx> > > My ack was on previous version where drvdata is set and used in same module. > https://www.spinics.net/lists/kvm/msg275737.html > > Its not a good practice to force vfio_pci_core vendor drivers to set a > particular structure pointer in drvdata. drvdata set from a driver > should be used by same driver and other driver should not assume/rely on it. > > I still prefer earlier version. Kirti, Do you still have an objection to your previous ack being carried forward? Thanks, Alex
