From a15ac665b9e9c90b1557499f2a46c1e89d29154a Mon Sep 17 00:00:00 2001 From: Eric Farman Date: Thu, 3 Dec 2020 22:35:11 +0100 Subject: vfio-mdev: Wire in a request handler for mdev parent While performing some destructive tests with vfio-ccw, where the paths to a device are forcible removed and thus the device itself is unreachable, it is rather easy to end up in an endless loop in vfio_del_group_dev() due to the lack of a request callback for the associated device. In this example, one MDEV (77c) is used by a guest, while another (77b) is not. The symptom is that the iommu is detached from the mdev for 77b, but not 77c, until that guest is shutdown: [ 238.794867] vfio_ccw 0.0.077b: MDEV: Unregistering [ 238.794996] vfio_mdev 11f2d2bc-4083-431d-a023-eff72715c4f0: Removing from iommu group 2 [ 238.795001] vfio_mdev 11f2d2bc-4083-431d-a023-eff72715c4f0: MDEV: detaching iommu [ 238.795036] vfio_ccw 0.0.077c: MDEV: Unregistering ...silence... Let's wire in the request call back to the mdev device, so that a device being physically removed from the host can be (gracefully?) handled by the parent device at the time the device is removed. Add a message when registering the device if a driver doesn't provide this callback, so a clue is given that this same loop may be encountered in a similar situation, and a message when this occurs instead of the awkward silence noted above. Signed-off-by: Eric Farman Reviewed-by: Cornelia Huck Signed-off-by: Alex Williamson --- drivers/vfio/mdev/mdev_core.c | 4 ++++ drivers/vfio/mdev/vfio_mdev.c | 13 +++++++++++++ 2 files changed, 17 insertions(+) (limited to 'drivers/vfio') diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c index b558d4cfd082..6de97d25a3f8 100644 --- a/drivers/vfio/mdev/mdev_core.c +++ b/drivers/vfio/mdev/mdev_core.c @@ -154,6 +154,10 @@ int mdev_register_device(struct device *dev, const struct mdev_parent_ops *ops) if (!dev) return -EINVAL; + /* Not mandatory, but its absence could be a problem */ + if (!ops->request) + dev_info(dev, "Driver cannot be asked to release device\n"); + mutex_lock(&parent_list_lock); /* Check for duplicate */ diff --git a/drivers/vfio/mdev/vfio_mdev.c b/drivers/vfio/mdev/vfio_mdev.c index 30964a4e0a28..b52eea128549 100644 --- a/drivers/vfio/mdev/vfio_mdev.c +++ b/drivers/vfio/mdev/vfio_mdev.c @@ -98,6 +98,18 @@ static int vfio_mdev_mmap(void *device_data, struct vm_area_struct *vma) return parent->ops->mmap(mdev, vma); } +static void vfio_mdev_request(void *device_data, unsigned int count) +{ + struct mdev_device *mdev = device_data; + struct mdev_parent *parent = mdev->parent; + + if (parent->ops->request) + parent->ops->request(mdev, count); + else if (count == 0) + dev_notice(mdev_dev(mdev), + "No mdev vendor driver request callback support, blocked until released by user\n"); +} + static const struct vfio_device_ops vfio_mdev_dev_ops = { .name = "vfio-mdev", .open = vfio_mdev_open, @@ -106,6 +118,7 @@ static const struct vfio_device_ops vfio_mdev_dev_ops = { .read = vfio_mdev_read, .write = vfio_mdev_write, .mmap = vfio_mdev_mmap, + .request = vfio_mdev_request, }; static int vfio_mdev_probe(struct device *dev) -- cgit v1.2.3