> -----Original Message----- > From: Alex Williamson [mailto:alex.williamson@xxxxxxxxxx] > Sent: Tuesday, May 12, 2015 7:42 PM > To: Allan, Bruce W > Cc: kvm@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; intel-wired- > lan@xxxxxxxxxxxxxxxx > Subject: Re: [PATCH] vfio-pci: PCI_DEV_FLAGS_ASSIGNED flag not set when > PCI device is assigned > > On Tue, 2015-05-12 at 18:35 -0700, Bruce Allan wrote: > > A number of PCI device drivers supporting SR-IOV use pci_vfs_assigned() > to > > check if there are any VF devices assigned by a VMM prior to disabling > > SR-IOV (i.e. bnx2x, be2net, fm10k, i40e, igb, ixgbe, qlcnic). This check > > works fine with the legacy device assignment (pci-stub enables the > device) > > which calls pci_set_dev_assigned(). The newer VFIO-based assignment > > (vfio-pci enables device) doesn't call pci_set_dev_assigned() potentially > > leading to issues in those drivers when disabling SR-IOV with VFs assigned. > > > > Add calls to pci_[set|clear]_dev_assigned() to set the flag as expected. > > > > Signed-off-by: Bruce Allan <bruce.w.allan@xxxxxxxxx> > > --- > > drivers/vfio/pci/vfio_pci.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > Why should a device exposed to the user be handled differently than a > device used by a host driver? The reason the assigned flag exists is > because legacy KVM device assignment doesn't actually claim the device > using the driver model, it relies on pci-stub to act as a placeholder to > prevent other drivers from binding to the device, but pci-stub has no > visibility to the device usage and will immediately release it > regardless of it being in use. vfio-pci participates in the driver > model, signals the user for the device to be released and blocks until > it is released. Beyond that, the assigned flag is a racy hack. There's > no locking whatsoever to imply that the flag as any meaning beyond the > instant that it's tested. I'd like to see the assigned flag deprecated > along with legacy KVM device assignment, not perpetuated in newer > drivers. The patch is also wrong because we can tell when the device is > actually opened by the user, not just bound to the vfio-pci driver. > Thanks, > > Alex So for clarification, in the drivers mentioned above would you recommend rather than checking pci_vfs_assigned() before disabling SR-IOV the drivers should instead check if any of the VF devices are bound/opened by another driver? Thanks, Bruce. ��.n��������+%������w��{.n�����o�^n�r������&��z�ޗ�zf���h���~����������_��+v���)ߣ�
