[PATCH v4 8/9] vfio/pci: Extend VFIO_DEVICE_GET_PCI_HOT_RESET_INFO for vfio device cdev

Yi Liu
2023-04-26T14:54:48Z

This makes VFIO_DEVICE_GET_PCI_HOT_RESET_INFO ioctl to use the bound
iommufd of the cdev device to check the ownership of the other affected
devices and set a flag to tell user if the cdev device is resettable
with a zero-length fd array.

For each of the affected devices, if it is bound to the iommufd of the
cdev device, _INFO reports a valid dev_id > 0; if it is not opened by
the calling user, but it is in the iommu_group of a device that is bound
to the iommufd of the cdev device, reports dev_id == 0; If the device is
un-owned device, configured within a different iommufd, or opened outside
of the vfio device cdev API, the _INFO ioctl shall report dev_id==-1 for
such affected devices. dev_id >=0 doesn't block hot-reset, while
dev_id == -1 will block hot-reset.

This adds flag VFIO_PCI_HOT_RESET_FLAG_IOMMUFD_DEV_ID to tell the user
dev_id is returned and adds flag VFIO_PCI_HOT_RESET_FLAG_RESETTABLE to
tell user if the cdev device is resettable or not.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Suggested-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
---
drivers/vfio/pci/vfio_pci_core.c | 101 ++++++++++++++++++++++++++++---
include/uapi/linux/vfio.h | 39 +++++++++++-
2 files changed, 132 insertions(+), 8 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index 39e7823088e7..43858d471447 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -766,6 +766,51 @@ static int vfio_pci_get_irq_count(struct vfio_pci_core_device *vdev, int irq_typ
return 0;
}

+static struct vfio_device *
+vfio_pci_find_device_in_devset(struct vfio_device_set *dev_set,
+ struct pci_dev *pdev)
+{
+ struct vfio_device *cur;
+
+ lockdep_assert_held(&dev_set->lock);
+
+ list_for_each_entry(cur, &dev_set->device_list, dev_set_list)
+ if (cur->dev == &pdev->dev)
+ return cur;
+ return NULL;
+}
+
+/*
+ * Check if a given iommu_group has been bound to an iommufd within a
+ * devset. Returns true if there is device in the devset which is in
+ * the input iommu_group and meanwhile bound to the input iommufd.
+ * Otherwise, returns false.
+ */
+static bool
+vfio_devset_iommufd_has_group(struct vfio_device_set *dev_set,
+ struct iommufd_ctx *iommufd,
+ struct iommu_group *iommu_group)
+{
+ struct vfio_device *cur;
+ struct iommu_group *grp;
+ bool found = false;
+
+ lockdep_assert_held(&dev_set->lock);
+
+ list_for_each_entry(cur, &dev_set->device_list, dev_set_list) {
+ grp = iommu_group_get(cur->dev);
+ if (!grp)
+ continue;
+ iommu_group_put(grp);
+ if (iommu_group == grp &&
+ iommufd == vfio_iommufd_physical_ictx(cur)) {
+ found = true;
+ break;
+ }
+ }
+ return found;
+}
+
static int vfio_pci_count_devs(struct pci_dev *pdev, void *data)
{
(*(int *)data)++;
@@ -776,13 +821,20 @@ struct vfio_pci_fill_info {
int max;
int cur;
struct vfio_pci_dependent_device *devices;
+ struct vfio_device *vdev;
+ bool devid;
+ bool resettable;
};

static int vfio_pci_fill_devs(struct pci_dev *pdev, void *data)
{
struct vfio_pci_fill_info *fill = data;
+ struct iommufd_ctx *iommufd = vfio_iommufd_physical_ictx(fill->vdev);
+ struct vfio_device_set *dev_set = fill->vdev->dev_set;
struct iommu_group *iommu_group;

+ lockdep_assert_held(&dev_set->lock);
+
if (fill->cur == fill->max)
return -EAGAIN; /* Something changed, try again */

@@ -790,7 +842,34 @@ static int vfio_pci_fill_devs(struct pci_dev *pdev, void *data)
if (!iommu_group)
return -EPERM; /* Cannot reset non-isolated devices */

- fill->devices[fill->cur].group_id = iommu_group_id(iommu_group);
+ if (fill->devid) {
+ struct vfio_device *vdev;
+
+ /*
+ * Report devid for the affected devices:
+ * - valid devid > 0 for the devices that are bound with
+ * the iommufd of the calling device.
+ * - devid == 0 for the devices that have not been opened
+ * but have same group with one of the devices bound to
+ * the iommufd of the calling device.
+ * - devid == -1 for others, and clear resettable flag.
+ */
+ vdev = vfio_pci_find_device_in_devset(dev_set, pdev);
+ if (vdev && iommufd == vfio_iommufd_physical_ictx(vdev)) {
+ fill->devices[fill->cur].dev_id =
+ vfio_iommufd_physical_devid(vdev);
+ if (unlikely(!fill->devices[fill->cur].dev_id))
+ return -EINVAL;
+ } else if (vfio_devset_iommufd_has_group(dev_set, iommufd,
+ iommu_group)) {
+ fill->devices[fill->cur].dev_id = VFIO_PCI_DEVID_NONBLOCKING;
+ } else {
+ fill->devices[fill->cur].dev_id = VFIO_PCI_DEVID_BLOCKING;
+ fill->resettable = false;
+ }
+ } else {
+ fill->devices[fill->cur].group_id = iommu_group_id(iommu_group);
+ }
fill->devices[fill->cur].segment = pci_domain_nr(pdev->bus);
fill->devices[fill->cur].bus = pdev->bus->number;
fill->devices[fill->cur].devfn = pdev->devfn;
@@ -1229,17 +1308,27 @@ static int vfio_pci_ioctl_get_pci_hot_reset_info(
return -ENOMEM;

fill.devices = devices;
+ fill.vdev = &vdev->vdev;

+ mutex_lock(&vdev->vdev.dev_set->lock);
+ fill.devid = fill.resettable = vfio_device_cdev_opened(&vdev->vdev);
ret = vfio_pci_for_each_slot_or_bus(vdev->pdev, vfio_pci_fill_devs,
&fill, slot);
+ mutex_unlock(&vdev->vdev.dev_set->lock);

/*
* If a device was removed between counting and filling, we may come up
* short of fill.max. If a device was added, we'll have a return of
* -EAGAIN above.
*/
- if (!ret)
+ if (!ret) {
hdr.count = fill.cur;
+ if (fill.devid) {
+ hdr.flags = VFIO_PCI_HOT_RESET_FLAG_IOMMUFD_DEV_ID;
+ if (fill.resettable)
+ hdr.flags |= VFIO_PCI_HOT_RESET_FLAG_RESETTABLE;
+ }
+ }

reset_info_exit:
if (copy_to_user(arg, &hdr, minsz))
@@ -2335,12 +2424,10 @@ static bool vfio_dev_in_groups(struct vfio_pci_core_device *vdev,
static int vfio_pci_is_device_in_set(struct pci_dev *pdev, void *data)
{
struct vfio_device_set *dev_set = data;
- struct vfio_device *cur;

- list_for_each_entry(cur, &dev_set->device_list, dev_set_list)
- if (cur->dev == &pdev->dev)
- return 0;
- return -EBUSY;
+ lockdep_assert_held(&dev_set->lock);
+
+ return vfio_pci_find_device_in_devset(dev_set, pdev) ? 0 : -EBUSY;
}

/*
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 0552e8dcf0cb..4b4e2c28984b 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -650,11 +650,46 @@ enum {
* VFIO_DEVICE_GET_PCI_HOT_RESET_INFO - _IOWR(VFIO_TYPE, VFIO_BASE + 12,
* struct vfio_pci_hot_reset_info)
*
+ * This command is used to query the affected devices in the hot reset for
+ * a given device.
+ *
+ * This command always reports the segment, bus, and devfn information for
+ * each affected device, and selectively reports the group_id or dev_id per
+ * the way how the calling device is opened.
+ *
+ * - If the calling device is opened via the traditional group/container
+ * API, group_id is reported. User should check if it has owned all
+ * the affected devices and provides a set of group fds to prove the
+ * ownership in VFIO_DEVICE_PCI_HOT_RESET ioctl.
+ *
+ * - If the calling device is opened as a cdev, dev_id is reported.
+ * Flag VFIO_PCI_HOT_RESET_FLAG_IOMMUFD_DEV_ID would be set. Flag
+ * VFIO_PCI_HOT_RESET_FLAG_RESETTABLE would be set per the ownership
+ * of the other affected devices. If it is set, the user could invoke
+ * VFIO_DEVICE_PCI_HOT_RESET with a zero-length fd array. Kernel
+ * set this flag when all the affected devices are owned by the user.
+ * This flag is available only VFIO_PCI_HOT_RESET_FLAG_IOMMUFD_DEV_ID
+ * is set, otherwise ignored. For a given affected device, it is owned
+ * if it suits one of the below cases:
+ * 1) bound to the same iommufd_ctx with the calling device
+ * 2) has not been bound to iommufd_ctx, but it is within the
+ * iommu_group of an owned device.
+ * For 1), the dev_id > 0, for 2) dev_id == 0. Otherwise, dev_id == -1.
+ *
+ * If the affected devices of a calling device span into multiple iommufds
+ * or opened by different APIs (group/container or cdev), hot-reset on
+ * this device would be rejected.
+ *
* Return: 0 on success, -errno on failure:
* -enospc = insufficient buffer, -enodev = unsupported for device.
*/
struct vfio_pci_dependent_device {
- __u32 group_id;
+ union {
+ __u32 group_id;
+ __u32 dev_id;
+#define VFIO_PCI_DEVID_NONBLOCKING 0
+#define VFIO_PCI_DEVID_BLOCKING -1
+ };
__u16 segment;
__u8 bus;
__u8 devfn; /* Use PCI_SLOT/PCI_FUNC */
@@ -663,6 +698,8 @@ struct vfio_pci_dependent_device {
struct vfio_pci_hot_reset_info {
__u32 argsz;
__u32 flags;
+#define VFIO_PCI_HOT_RESET_FLAG_IOMMUFD_DEV_ID (1 << 0)
+#define VFIO_PCI_HOT_RESET_FLAG_RESETTABLE (1 << 1)
__u32 count;
struct vfio_pci_dependent_device devices[];
};
--
2.34.1