From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:4476 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726698AbgKQDVr (ORCPT ); Mon, 16 Nov 2020 22:21:47 -0500 From: Eric Farman Subject: [RFC PATCH 1/2] vfio-mdev: Wire in a request handler for mdev parent Date: Tue, 17 Nov 2020 04:21:38 +0100 Message-Id: <20201117032139.50988-2-farman@linux.ibm.com> In-Reply-To: <20201117032139.50988-1-farman@linux.ibm.com> References: <20201117032139.50988-1-farman@linux.ibm.com> List-ID: To: Cornelia Huck , Kirti Wankhede , Alex Williamson Cc: Halil Pasic , linux-s390@vger.kernel.org, kvm@vger.kernel.org, Eric Farman 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 hot unplug can be (gracefully?) handled by the parent device at the time the device is being removed. Signed-off-by: Eric Farman --- drivers/vfio/mdev/vfio_mdev.c | 11 +++++++++++ include/linux/mdev.h | 4 ++++ 2 files changed, 15 insertions(+) diff --git a/drivers/vfio/mdev/vfio_mdev.c b/drivers/vfio/mdev/vfio_mdev.c index 30964a4e0a28..2dd243f73945 100644 --- a/drivers/vfio/mdev/vfio_mdev.c +++ b/drivers/vfio/mdev/vfio_mdev.c @@ -98,6 +98,16 @@ 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 (unlikely(!parent->ops->request)) + return; + parent->ops->request(mdev, count); +} + static const struct vfio_device_ops vfio_mdev_dev_ops = { .name = "vfio-mdev", .open = vfio_mdev_open, @@ -106,6 +116,7 @@ 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) diff --git a/include/linux/mdev.h b/include/linux/mdev.h index 0ce30ca78db0..0ed88be1f4bb 100644 --- a/include/linux/mdev.h +++ b/include/linux/mdev.h @@ -72,6 +72,9 @@ struct device *mdev_get_iommu_device(struct device *dev); * @mmap: mmap callback * @mdev: mediated device structure * @vma: vma structure + * @request: request callback + * @mdev: mediated device structure + * @count: request sequence number * Parent device that support mediated device should be registered with mdev * module with mdev_parent_ops structure. **/ @@ -92,6 +95,7 @@ struct mdev_parent_ops { long (*ioctl)(struct mdev_device *mdev, unsigned int cmd, unsigned long arg); int (*mmap)(struct mdev_device *mdev, struct vm_area_struct *vma); + void (*request)(struct mdev_device *mdev, unsigned int count); }; /* interface for exporting mdev supported type attributes */ -- 2.17.1