On Thu, 10 Nov 2022 11:03:29 +0800 Yi Liu <yi.l.liu@xxxxxxxxx> wrote: > Hi DeRossi, > > On 2022/11/10 09:40, Anthony DeRossi wrote: > > vfio_pci_dev_set_needs_reset() inspects the open_count of every device > > in the set to determine whether a reset is allowed. The current device > > always has open_count == 1 within vfio_pci_core_disable(), effectively > > disabling the reset logic. This field is also documented as private in > > vfio_device, so it should not be used to determine whether other devices > > in the set are open. > > haven't went through the prior version. maybe may question has been already > answered. My question is: > > the major reason is the order problem in vfio_main.c. close_device() is > always called before decreasing open_count to be 0. So even other device > has no open fd, the current vfio_device still have one open count. So why > can't we just switch the order of open_count-- and close_device()? This is what was originally proposed and Jason shot it down: https://lore.kernel.org/all/Y1kY0I4lr7KntbWp@xxxxxxxx/ > > Checking for vfio_device_set_open_count() > 1 on the device set fixes > > both issues > tbh. it's weird to me that a driver needs to know the internal logic of > vfio core before knowing it needs to check the vfio_device_set_open_count() > in this way. Is vfio-pci the only driver that needs to do this check or > there are other drivers? If there are other drivers, maybe fixing the order > in core is better. Please see the evolution of reflck into device sets. Both PCI and FSL can have multiple devices in a set, AIUI. The driver defines the set. This ability to test for the last close among devices in the set is a fundamental feature of the original reflck. Thanks, Alex
