[PATCH v4 9/9] vfio/pci: Allow passing zero-length fd array in VFIO_DEVICE_PCI_HOT_RESET

Yi Liu
2023-04-26T14:54:57Z

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_RESETTABLE
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 | 66 +++++++++++++++++++++++++++-----
include/uapi/linux/vfio.h | 22 +++++++++++
2 files changed, 79 insertions(+), 9 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index 43858d471447..f70e3b948b16 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -180,7 +180,8 @@ 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
@@ -1364,8 +1365,7 @@ 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);
@@ -1414,7 +1414,7 @@ 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--)
@@ -1429,6 +1429,7 @@ static int vfio_pci_ioctl_pci_hot_reset(struct vfio_pci_core_device *vdev,
{
unsigned long minsz = offsetofend(struct vfio_pci_hot_reset, count);
struct vfio_pci_hot_reset hdr;
+ struct iommufd_ctx *iommufd;
bool slot = false;

if (copy_from_user(&hdr, arg, minsz))
@@ -1443,7 +1444,12 @@ static int vfio_pci_ioctl_pci_hot_reset(struct vfio_pci_core_device *vdev,
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);
+
+ iommufd = vfio_iommufd_physical_ictx(&vdev->vdev);
+
+ return vfio_pci_dev_set_hot_reset(vdev->vdev.dev_set, NULL, iommufd);
}

static int vfio_pci_ioctl_ioeventfd(struct vfio_pci_core_device *vdev,
@@ -2415,6 +2421,9 @@ static bool vfio_dev_in_groups(struct vfio_pci_core_device *vdev,
{
unsigned int i;

+ if (!groups)
+ return false;
+
for (i = 0; i < groups->count; i++)
if (vfio_file_has_dev(groups->files[i], &vdev->vdev))
return true;
@@ -2488,13 +2497,38 @@ static int vfio_pci_dev_set_pm_runtime_get(struct vfio_device_set *dev_set)
return ret;
}

+static bool vfio_dev_in_iommufd_ctx(struct vfio_pci_core_device *vdev,
+ struct iommufd_ctx *iommufd_ctx)
+{
+ struct iommufd_ctx *iommufd = vfio_iommufd_physical_ictx(&vdev->vdev);
+ struct iommu_group *iommu_group;
+
+ if (!iommufd_ctx)
+ return false;
+
+ if (iommufd == iommufd_ctx)
+ return true;
+
+ iommu_group = iommu_group_get(vdev->vdev.dev);
+ if (!iommu_group)
+ return false;
+
+ /*
+ * Try to check if any device within iommu_group is bound with
+ * the input iommufd_ctx.
+ */
+ return vfio_devset_iommufd_has_group(vdev->vdev.dev_set,
+ iommufd_ctx, iommu_group);
+}
+
/*
* We need to get memory_lock for each device, but devices can share mmap_lock,
* therefore we need to zap and hold the vma_lock for each device, and only then
* 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;
@@ -2525,10 +2559,24 @@ static int vfio_pci_dev_set_hot_reset(struct vfio_device_set *dev_set,

list_for_each_entry(cur_vma, &dev_set->device_list, vdev.dev_set_list) {
/*
- * 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 user provides a set of groups, all the opened devices
+ * in the dev_set should be contained by the set of groups
+ * provided by the user.
+ *
+ * If user provides a zero-length group fd array, then all
+ * the affected devices must be bound to same iommufd_ctx as
+ * the input iommufd_ctx. If there is device that has not
+ * been bound to iommufd_ctx yet, shall check if there is any
+ * device within its iommu_group that has been bound to the
+ * input iommufd_ctx.
+ *
+ * Otherwise, reset is not allowed.
*/
- if (!vfio_dev_in_groups(cur_vma, groups)) {
+ if (!vfio_dev_in_groups(cur_vma, groups) &&
+ !vfio_dev_in_iommufd_ctx(cur_vma, iommufd_ctx)) {
ret = -EINVAL;
goto err_undo;
}
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 4b4e2c28984b..1241d02d8701 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -710,6 +710,28 @@ struct vfio_pci_hot_reset_info {
* VFIO_DEVICE_PCI_HOT_RESET - _IOW(VFIO_TYPE, VFIO_BASE + 13,
* struct vfio_pci_hot_reset)
*
+ * Userspace requests hot reset for the devices it operates. Due to the
+ * underlying topology, multiple devices can be affected in the reset
+ * while some might be opened by another user. To avoid interference
+ * the calling user must ensure all affected devices are owned by itself.
+ * The ownership proof needs to refer the output of
+ * VFIO_DEVICE_GET_PCI_HOT_RESET_INFO. Ownership can be proved as:
+ *
+ * 1) An array of group fds - This is used for the devices opened via
+ * the group/container interface.
+ * 2) A zero-length array - This is used for the devices opened via
+ * the cdev interface. User should check the
+ * flag VFIO_PCI_HOT_RESET_FLAG_IOMMUFD_DEV_ID
+ * and flag VFIO_PCI_HOT_RESET_FLAG_RESETTABLE
+ * before using this method.
+ *
+ * In case a non void group fd array is passed, the devices affected by
+ * the reset must belong to those opened VFIO groups. In case a zero
+ * length array is passed, the other devices affected by the reset, if
+ * any, must be either bound to the same iommufd as this VFIO device or
+ * in the same iommu_group with a device that does. Either of the two
+ * methods is applied to check the feasibility of the hot reset.
+ *
* Return: 0 on success, -errno on failure.
*/
struct vfio_pci_hot_reset {
--
2.34.1