Messages in this thread | | | Date | Fri, 20 May 2022 09:56:45 -0400 | Subject | Re: [PATCH v3 1/1] vfio: remove VFIO_GROUP_NOTIFY_SET_KVM | From | Tony Krowiak <> |
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On 5/19/22 2:33 PM, Matthew Rosato wrote: > Rather than relying on a notifier for associating the KVM with > the group, let's assume that the association has already been > made prior to device_open. The first time a device is opened > associate the group KVM with the device. > > This fixes a user-triggerable oops in GVT. > > Reviewed-by: Tony Krowiak <akrowiak@linux.ibm.com> > Reviewed-by: Kevin Tian <kevin.tian@intel.com> > Reviewed-by: Christoph Hellwig <hch@lst.de> > Signed-off-by: Jason Gunthorpe <jgg@nvidia.com> > Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com> > --- > drivers/gpu/drm/i915/gvt/gtt.c | 4 +- > drivers/gpu/drm/i915/gvt/gvt.h | 3 - > drivers/gpu/drm/i915/gvt/kvmgt.c | 82 ++++++-------------------- > drivers/s390/crypto/vfio_ap_ops.c | 35 ++--------- > drivers/s390/crypto/vfio_ap_private.h | 3 - > drivers/vfio/vfio.c | 83 ++++++++++----------------- > include/linux/vfio.h | 6 +- > 7 files changed, 57 insertions(+), 159 deletions(-) > > > > diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c > index e8914024f5b1..a7d2a95796d3 100644 > --- a/drivers/s390/crypto/vfio_ap_ops.c > +++ b/drivers/s390/crypto/vfio_ap_ops.c > @@ -1284,25 +1284,6 @@ static void vfio_ap_mdev_unset_kvm(struct ap_matrix_mdev *matrix_mdev) > } > } > > -static int vfio_ap_mdev_group_notifier(struct notifier_block *nb, > - unsigned long action, void *data) > -{ > - int notify_rc = NOTIFY_OK; > - struct ap_matrix_mdev *matrix_mdev; > - > - if (action != VFIO_GROUP_NOTIFY_SET_KVM) > - return NOTIFY_OK; > - > - matrix_mdev = container_of(nb, struct ap_matrix_mdev, group_notifier); > - > - if (!data) > - vfio_ap_mdev_unset_kvm(matrix_mdev); > - else if (vfio_ap_mdev_set_kvm(matrix_mdev, data)) > - notify_rc = NOTIFY_DONE; > - > - return notify_rc; > -} > - > static struct vfio_ap_queue *vfio_ap_find_queue(int apqn) > { > struct device *dev; > @@ -1402,11 +1383,10 @@ static int vfio_ap_mdev_open_device(struct vfio_device *vdev) > unsigned long events; > int ret; > > - matrix_mdev->group_notifier.notifier_call = vfio_ap_mdev_group_notifier; > - events = VFIO_GROUP_NOTIFY_SET_KVM; > + if (!vdev->kvm) > + return -EINVAL; > > - ret = vfio_register_notifier(vdev, VFIO_GROUP_NOTIFY, &events, > - &matrix_mdev->group_notifier); > + ret = vfio_ap_mdev_set_kvm(matrix_mdev, vdev->kvm); > if (ret) > return ret;
I'm sorry I didn't see this with my last review, but maybe move the call to vfio_ap_mdev_set_kvm(matrix_mdev, vdev->kvm) after the successful registration of the IOMMU notifier? This way you won't be plugging AP queues into the guest only to remove them if the registration fails.
> > @@ -1415,12 +1395,11 @@ static int vfio_ap_mdev_open_device(struct vfio_device *vdev) > ret = vfio_register_notifier(vdev, VFIO_IOMMU_NOTIFY, &events, > &matrix_mdev->iommu_notifier); > if (ret) > - goto out_unregister_group; > + goto err_kvm; > return 0; > > -out_unregister_group: > - vfio_unregister_notifier(vdev, VFIO_GROUP_NOTIFY, > - &matrix_mdev->group_notifier); > +err_kvm: > + vfio_ap_mdev_unset_kvm(matrix_mdev); > return ret; > } > > @@ -1431,8 +1410,6 @@ static void vfio_ap_mdev_close_device(struct vfio_device *vdev) > > vfio_unregister_notifier(vdev, VFIO_IOMMU_NOTIFY, > &matrix_mdev->iommu_notifier); > - vfio_unregister_notifier(vdev, VFIO_GROUP_NOTIFY, > - &matrix_mdev->group_notifier); > vfio_ap_mdev_unset_kvm(matrix_mdev); > } > > diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h > index 648fcaf8104a..a26efd804d0d 100644 > --- a/drivers/s390/crypto/vfio_ap_private.h > +++ b/drivers/s390/crypto/vfio_ap_private.h > @@ -81,8 +81,6 @@ struct ap_matrix { > * @node: allows the ap_matrix_mdev struct to be added to a list > * @matrix: the adapters, usage domains and control domains assigned to the > * mediated matrix device. > - * @group_notifier: notifier block used for specifying callback function for > - * handling the VFIO_GROUP_NOTIFY_SET_KVM event > * @iommu_notifier: notifier block used for specifying callback function for > * handling the VFIO_IOMMU_NOTIFY_DMA_UNMAP even > * @kvm: the struct holding guest's state > @@ -94,7 +92,6 @@ struct ap_matrix_mdev { > struct vfio_device vdev; > struct list_head node; > struct ap_matrix matrix; > - struct notifier_block group_notifier; > struct notifier_block iommu_notifier; > struct kvm *kvm; > crypto_hook pqap_hook; > diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c > index cfcff7764403..831fc722e3f8 100644 > --- a/drivers/vfio/vfio.c > +++ b/drivers/vfio/vfio.c > @@ -1083,10 +1083,21 @@ static struct file *vfio_device_open(struct vfio_device *device) > > mutex_lock(&device->dev_set->lock); > device->open_count++; > - if (device->open_count == 1 && device->ops->open_device) { > - ret = device->ops->open_device(device); > - if (ret) > - goto err_undo_count; > + if (device->open_count == 1) { > + /* > + * Here we pass the KVM pointer with the group under the read > + * lock. If the device driver will use it, it must obtain a > + * reference and release it during close_device. > + */ > + down_read(&device->group->group_rwsem); > + device->kvm = device->group->kvm; > + > + if (device->ops->open_device) { > + ret = device->ops->open_device(device); > + if (ret) > + goto err_undo_count; > + } > + up_read(&device->group->group_rwsem); > } > mutex_unlock(&device->dev_set->lock); > > @@ -1119,10 +1130,14 @@ static struct file *vfio_device_open(struct vfio_device *device) > > err_close_device: > mutex_lock(&device->dev_set->lock); > + down_read(&device->group->group_rwsem); > if (device->open_count == 1 && device->ops->close_device) > device->ops->close_device(device); > err_undo_count: > device->open_count--; > + if (device->open_count == 0 && device->kvm) > + device->kvm = NULL; > + up_read(&device->group->group_rwsem); > mutex_unlock(&device->dev_set->lock); > module_put(device->dev->driver->owner); > err_unassign_container: > @@ -1315,9 +1330,13 @@ static int vfio_device_fops_release(struct inode *inode, struct file *filep) > > mutex_lock(&device->dev_set->lock); > vfio_assert_device_open(device); > + down_read(&device->group->group_rwsem); > if (device->open_count == 1 && device->ops->close_device) > device->ops->close_device(device); > + up_read(&device->group->group_rwsem); > device->open_count--; > + if (device->open_count == 0) > + device->kvm = NULL; > mutex_unlock(&device->dev_set->lock); > > module_put(device->dev->driver->owner); > @@ -1726,8 +1745,8 @@ EXPORT_SYMBOL_GPL(vfio_file_enforced_coherent); > * @file: VFIO group file > * @kvm: KVM to link > * > - * The kvm pointer will be forwarded to all the vfio_device's attached to the > - * VFIO file via the VFIO_GROUP_NOTIFY_SET_KVM notifier. > + * When a VFIO device is first opened the KVM will be available in > + * device->kvm if one was associated with the group. > */ > void vfio_file_set_kvm(struct file *file, struct kvm *kvm) > { > @@ -1738,8 +1757,6 @@ void vfio_file_set_kvm(struct file *file, struct kvm *kvm) > > down_write(&group->group_rwsem); > group->kvm = kvm; > - blocking_notifier_call_chain(&group->notifier, > - VFIO_GROUP_NOTIFY_SET_KVM, kvm); > up_write(&group->group_rwsem); > } > EXPORT_SYMBOL_GPL(vfio_file_set_kvm); > @@ -2006,7 +2023,8 @@ static int vfio_register_iommu_notifier(struct vfio_group *group, > struct vfio_iommu_driver *driver; > int ret; > > - down_read(&group->group_rwsem); > + lockdep_assert_held_read(&group->group_rwsem); > + > container = group->container; > driver = container->iommu_driver; > if (likely(driver && driver->ops->register_notifier)) > @@ -2014,7 +2032,6 @@ static int vfio_register_iommu_notifier(struct vfio_group *group, > events, nb); > else > ret = -ENOTTY; > - up_read(&group->group_rwsem); > > return ret; > } > @@ -2026,7 +2043,8 @@ static int vfio_unregister_iommu_notifier(struct vfio_group *group, > struct vfio_iommu_driver *driver; > int ret; > > - down_read(&group->group_rwsem); > + lockdep_assert_held_read(&group->group_rwsem); > + > container = group->container; > driver = container->iommu_driver; > if (likely(driver && driver->ops->unregister_notifier)) > @@ -2034,47 +2052,10 @@ static int vfio_unregister_iommu_notifier(struct vfio_group *group, > nb); > else > ret = -ENOTTY; > - up_read(&group->group_rwsem); > > return ret; > } > > -static int vfio_register_group_notifier(struct vfio_group *group, > - unsigned long *events, > - struct notifier_block *nb) > -{ > - int ret; > - bool set_kvm = false; > - > - if (*events & VFIO_GROUP_NOTIFY_SET_KVM) > - set_kvm = true; > - > - /* clear known events */ > - *events &= ~VFIO_GROUP_NOTIFY_SET_KVM; > - > - /* refuse to continue if still events remaining */ > - if (*events) > - return -EINVAL; > - > - ret = blocking_notifier_chain_register(&group->notifier, nb); > - if (ret) > - return ret; > - > - /* > - * The attaching of kvm and vfio_group might already happen, so > - * here we replay once upon registration. > - */ > - if (set_kvm) { > - down_read(&group->group_rwsem); > - if (group->kvm) > - blocking_notifier_call_chain(&group->notifier, > - VFIO_GROUP_NOTIFY_SET_KVM, > - group->kvm); > - up_read(&group->group_rwsem); > - } > - return 0; > -} > - > int vfio_register_notifier(struct vfio_device *device, > enum vfio_notify_type type, unsigned long *events, > struct notifier_block *nb) > @@ -2090,9 +2071,6 @@ int vfio_register_notifier(struct vfio_device *device, > case VFIO_IOMMU_NOTIFY: > ret = vfio_register_iommu_notifier(group, events, nb); > break; > - case VFIO_GROUP_NOTIFY: > - ret = vfio_register_group_notifier(group, events, nb); > - break; > default: > ret = -EINVAL; > } > @@ -2114,9 +2092,6 @@ int vfio_unregister_notifier(struct vfio_device *device, > case VFIO_IOMMU_NOTIFY: > ret = vfio_unregister_iommu_notifier(group, nb); > break; > - case VFIO_GROUP_NOTIFY: > - ret = blocking_notifier_chain_unregister(&group->notifier, nb); > - break; > default: > ret = -EINVAL; > } > diff --git a/include/linux/vfio.h b/include/linux/vfio.h > index 45b287826ce6..aa888cc51757 100644 > --- a/include/linux/vfio.h > +++ b/include/linux/vfio.h > @@ -36,6 +36,8 @@ struct vfio_device { > struct vfio_device_set *dev_set; > struct list_head dev_set_list; > unsigned int migration_flags; > + /* Driver must reference the kvm during open_device or never touch it */ > + struct kvm *kvm; > > /* Members below here are private, not for driver use */ > refcount_t refcount; > @@ -155,15 +157,11 @@ extern int vfio_dma_rw(struct vfio_device *device, dma_addr_t user_iova, > /* each type has independent events */ > enum vfio_notify_type { > VFIO_IOMMU_NOTIFY = 0, > - VFIO_GROUP_NOTIFY = 1, > }; > > /* events for VFIO_IOMMU_NOTIFY */ > #define VFIO_IOMMU_NOTIFY_DMA_UNMAP BIT(0) > > -/* events for VFIO_GROUP_NOTIFY */ > -#define VFIO_GROUP_NOTIFY_SET_KVM BIT(0) > - > extern int vfio_register_notifier(struct vfio_device *device, > enum vfio_notify_type type, > unsigned long *required_events,
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