vfio: Protect vfio_dev_present against device_del
vfio_dev_present is meant to give us a wait_event callback so that we can block removing a device from vfio until it becomes unused. The root of this check depends on being able to get the iommu group from the device. Unfortunately if the BUS_NOTIFY_DEL_DEVICE notifier has fired then the device-group reference is no longer searchable and we fail the lookup. We don't need to go to such extents for this though. We have a reference to the device, from which we can acquire a reference to the group. We can then use the group reference to search for the device and properly block removal. Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
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@ -642,33 +642,16 @@ int vfio_add_group_dev(struct device *dev,
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}
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EXPORT_SYMBOL_GPL(vfio_add_group_dev);
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/* Test whether a struct device is present in our tracking */
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static bool vfio_dev_present(struct device *dev)
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/* Given a referenced group, check if it contains the device */
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static bool vfio_dev_present(struct vfio_group *group, struct device *dev)
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{
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struct iommu_group *iommu_group;
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struct vfio_group *group;
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struct vfio_device *device;
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iommu_group = iommu_group_get(dev);
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if (!iommu_group)
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return false;
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group = vfio_group_get_from_iommu(iommu_group);
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if (!group) {
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iommu_group_put(iommu_group);
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return false;
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}
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device = vfio_group_get_device(group, dev);
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if (!device) {
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vfio_group_put(group);
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iommu_group_put(iommu_group);
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if (!device)
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return false;
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}
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vfio_device_put(device);
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vfio_group_put(group);
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iommu_group_put(iommu_group);
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return true;
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}
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@ -682,10 +665,18 @@ void *vfio_del_group_dev(struct device *dev)
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struct iommu_group *iommu_group = group->iommu_group;
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void *device_data = device->device_data;
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/*
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* The group exists so long as we have a device reference. Get
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* a group reference and use it to scan for the device going away.
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*/
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vfio_group_get(group);
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vfio_device_put(device);
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/* TODO send a signal to encourage this to be released */
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wait_event(vfio.release_q, !vfio_dev_present(dev));
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wait_event(vfio.release_q, !vfio_dev_present(group, dev));
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vfio_group_put(group);
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iommu_group_put(iommu_group);
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