[PATCH v8 10/10] vfio/pci: Allow passing zero-length fd array in VFIO_DEVICE_PCI_HOT_RESET

Yi Liu
2023-06-16T09:31:25Z

This is the way user to invoke hot-reset for the devices opened by cdev
interface. User should check the flag VFIO_PCI_HOT_RESET_FLAG_DEV_ID_OWNED
in the output of VFIO_DEVICE_GET_PCI_HOT_RESET_INFO ioctl before doing
hot-reset for cdev devices.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Tested-by: Yanting Jiang <yanting.jiang@intel.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
---
drivers/vfio/pci/vfio_pci_core.c | 61 ++++++++++++++++++++++++++------
include/uapi/linux/vfio.h | 21 +++++++++++
2 files changed, 71 insertions(+), 11 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index 5998da0f5771..860f8119ec9f 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -181,7 +181,8 @@ static void vfio_pci_probe_mmaps(struct vfio_pci_core_device *vdev)
struct vfio_pci_group_info;
static void vfio_pci_dev_set_try_reset(struct vfio_device_set *dev_set);
static int vfio_pci_dev_set_hot_reset(struct vfio_device_set *dev_set,
- struct vfio_pci_group_info *groups);
+ struct vfio_pci_group_info *groups,
+ struct iommufd_ctx *iommufd_ctx);

/*
* INTx masking requires the ability to disable INTx signaling via PCI_COMMAND
@@ -1291,8 +1292,7 @@ vfio_pci_ioctl_pci_hot_reset_groups(struct vfio_pci_core_device *vdev,
if (ret)
return ret;

- /* Somewhere between 1 and count is OK */
- if (!array_count || array_count > count)
+ if (array_count > count)
return -EINVAL;

group_fds = kcalloc(array_count, sizeof(*group_fds), GFP_KERNEL);
@@ -1341,7 +1341,7 @@ vfio_pci_ioctl_pci_hot_reset_groups(struct vfio_pci_core_device *vdev,
info.count = array_count;
info.files = files;

- ret = vfio_pci_dev_set_hot_reset(vdev->vdev.dev_set, &info);
+ ret = vfio_pci_dev_set_hot_reset(vdev->vdev.dev_set, &info, NULL);

hot_reset_release:
for (file_idx--; file_idx >= 0; file_idx--)
@@ -1364,13 +1364,21 @@ static int vfio_pci_ioctl_pci_hot_reset(struct vfio_pci_core_device *vdev,
if (hdr.argsz < minsz || hdr.flags)
return -EINVAL;

+ /* zero-length array is only for cdev opened devices */
+ if (!!hdr.count == vfio_device_cdev_opened(&vdev->vdev))
+ return -EINVAL;
+
/* Can we do a slot or bus reset or neither? */
if (!pci_probe_reset_slot(vdev->pdev->slot))
slot = true;
else if (pci_probe_reset_bus(vdev->pdev->bus))
return -ENODEV;

- return vfio_pci_ioctl_pci_hot_reset_groups(vdev, hdr.count, slot, arg);
+ if (hdr.count)
+ return vfio_pci_ioctl_pci_hot_reset_groups(vdev, hdr.count, slot, arg);
+
+ return vfio_pci_dev_set_hot_reset(vdev->vdev.dev_set, NULL,
+ vfio_iommufd_device_ictx(&vdev->vdev));
}

static int vfio_pci_ioctl_ioeventfd(struct vfio_pci_core_device *vdev,
@@ -2338,13 +2346,16 @@ const struct pci_error_handlers vfio_pci_core_err_handlers = {
};
EXPORT_SYMBOL_GPL(vfio_pci_core_err_handlers);

-static bool vfio_dev_in_groups(struct vfio_pci_core_device *vdev,
+static bool vfio_dev_in_groups(struct vfio_device *vdev,
struct vfio_pci_group_info *groups)
{
unsigned int i;

+ if (!groups)
+ return false;
+
for (i = 0; i < groups->count; i++)
- if (vfio_file_has_dev(groups->files[i], &vdev->vdev))
+ if (vfio_file_has_dev(groups->files[i], vdev))
return true;
return false;
}
@@ -2420,7 +2431,8 @@ static int vfio_pci_dev_set_pm_runtime_get(struct vfio_device_set *dev_set)
* get each memory_lock.
*/
static int vfio_pci_dev_set_hot_reset(struct vfio_device_set *dev_set,
- struct vfio_pci_group_info *groups)
+ struct vfio_pci_group_info *groups,
+ struct iommufd_ctx *iommufd_ctx)
{
struct vfio_pci_core_device *cur_mem;
struct vfio_pci_core_device *cur_vma;
@@ -2450,11 +2462,38 @@ static int vfio_pci_dev_set_hot_reset(struct vfio_device_set *dev_set,
goto err_unlock;

list_for_each_entry(cur_vma, &dev_set->device_list, vdev.dev_set_list) {
+ bool owned;
+
/*
- * Test whether all the affected devices are contained by the
- * set of groups provided by the user.
+ * Test whether all the affected devices can be reset by the
+ * user.
+ *
+ * If called from a group opened device and the user provides
+ * a set of groups, all the devices in the dev_set should be
+ * contained by the set of groups provided by the user.
+ *
+ * If called from a cdev opened device and the user provides
+ * a zero-length array, all the devices in the dev_set must
+ * be bound to the same iommufd_ctx as the input iommufd_ctx.
+ * If there is any device that has not been bound to any
+ * iommufd_ctx yet, check if its iommu_group has any device
+ * bound to the input iommufd_ctx. Such devices can be
+ * considered owned by the input iommufd_ctx as the device
+ * cannot be owned by another iommufd_ctx when its iommu_group
+ * is owned.
+ *
+ * Otherwise, reset is not allowed.
*/
- if (!vfio_dev_in_groups(cur_vma, groups)) {
+ if (iommufd_ctx) {
+ int devid = vfio_iommufd_get_dev_id(&cur_vma->vdev,
+ iommufd_ctx);
+
+ owned = (devid > 0 || devid == -ENOENT);
+ } else {
+ owned = vfio_dev_in_groups(&cur_vma->vdev, groups);
+ }
+
+ if (!owned) {
ret = -EINVAL;
goto err_undo;
}
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index d7deb5acad62..e2c01bc01761 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -693,6 +693,9 @@ enum {
* affected devices are represented in the dev_set and also owned by
* the user. This flag is available only when
* flag VFIO_PCI_HOT_RESET_FLAG_DEV_ID is set, otherwise reserved.
+ * When set, user could invoke VFIO_DEVICE_PCI_HOT_RESET with a zero
+ * length fd array on the calling device as the ownership is validated
+ * by iommufd_ctx.
*
* Return: 0 on success, -errno on failure:
* -enospc = insufficient buffer, -enodev = unsupported for device.
@@ -724,6 +727,24 @@ struct vfio_pci_hot_reset_info {
* VFIO_DEVICE_PCI_HOT_RESET - _IOW(VFIO_TYPE, VFIO_BASE + 13,
* struct vfio_pci_hot_reset)
*
+ * A PCI hot reset results in either a bus or slot reset which may affect
+ * other devices sharing the bus/slot. The calling user must have
+ * ownership of the full set of affected devices as determined by the
+ * VFIO_DEVICE_GET_PCI_HOT_RESET_INFO ioctl.
+ *
+ * When called on a device file descriptor acquired through the vfio
+ * group interface, the user is required to provide proof of ownership
+ * of those affected devices via the group_fds array in struct
+ * vfio_pci_hot_reset.
+ *
+ * When called on a direct cdev opened vfio device, the flags field of
+ * struct vfio_pci_hot_reset_info reports the ownership status of the
+ * affected devices and this ioctl must be called with an empty group_fds
+ * array. See above INFO ioctl definition for ownership requirements.
+ *
+ * Mixed usage of legacy groups and cdevs across the set of affected
+ * devices is not supported.
+ *
* Return: 0 on success, -errno on failure.
*/
struct vfio_pci_hot_reset {
--
2.34.1