[PATCH v5 09/10] vfio/pci: Extend VFIO_DEVICE_GET_PCI_HOT_RESET_INFO for vfio device cdev

[Yi Liu <yi.l.liu@intel.com>]

This makes VFIO_DEVICE_GET_PCI_HOT_RESET_INFO ioctl to use the iommufd_ctx
of the cdev device to check the ownership of the other affected devices.

This returns devid for each of the affected devices. If it is bound to the
iommufd_ctx of the cdev device, _INFO reports a valid devid > 0; If it is
not opened by the calling user, but it belongs to the same iommu_group of
a device that is bound to the iommufd_ctx of the cdev device, reports devid
value of 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 devid value of -1.

devid >=0 doesn't block hot-reset as the affected devices are considered to
be owned, while devid == -1 will block the use of VFIO_DEVICE_PCI_HOT_RESET
outside of proof-of-ownership calling conventions (ie. via legacy group
accessed devices).

This adds flag VFIO_PCI_HOT_RESET_FLAG_DEV_ID to tell the user devid is
returned in case of calling user get device fd from other software stack
and adds flag VFIO_PCI_HOT_RESET_FLAG_DEV_ID_OWNED to tell user if all
the affected devices are owned, so user can know it without looping all
the returned devids.

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 | 52 ++++++++++++++++++++++++++++++--
 include/uapi/linux/vfio.h        | 46 +++++++++++++++++++++++++++-
 2 files changed, 95 insertions(+), 3 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index 4df2def35bdd..57586be770af 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -27,6 +27,7 @@
 #include <linux/vgaarb.h>
 #include <linux/nospec.h>
 #include <linux/sched/mm.h>
+#include <linux/iommufd.h>
 #if IS_ENABLED(CONFIG_EEH)
 #include <asm/eeh.h>
 #endif
@@ -36,6 +37,10 @@
 #define DRIVER_AUTHOR   "Alex Williamson <alex.williamson@redhat.com>"
 #define DRIVER_DESC "core driver for VFIO based PCI devices"
 
+#ifdef CONFIG_IOMMUFD
+MODULE_IMPORT_NS(IOMMUFD);
+#endif
+
 static bool nointxmask;
 static bool disable_vga;
 static bool disable_idle_d3;
@@ -776,6 +781,9 @@ struct vfio_pci_fill_info {
 	int max;
 	int cur;
 	struct vfio_pci_dependent_device *devices;
+	struct vfio_device *vdev;
+	bool devid:1;
+	bool dev_owned:1;
 };
 
 static int vfio_pci_fill_devs(struct pci_dev *pdev, void *data)
@@ -790,7 +798,37 @@ 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 iommufd_ctx *iommufd = vfio_iommufd_physical_ictx(fill->vdev);
+		struct vfio_device_set *dev_set = fill->vdev->dev_set;
+		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 dev_owned flag.
+		 */
+		vdev = vfio_find_device_in_devset(dev_set, &pdev->dev);
+		if (vdev && iommufd == vfio_iommufd_physical_ictx(vdev)) {
+			int ret;
+
+			ret = vfio_iommufd_physical_devid(vdev);
+			if (WARN_ON(ret < 0))
+				return ret;
+			fill->devices[fill->cur].devid = ret;
+		} else if (vdev && iommufd_ctx_has_group(iommufd, iommu_group)) {
+			fill->devices[fill->cur].devid = VFIO_PCI_DEVID_OWNED;
+		} else {
+			fill->devices[fill->cur].devid = VFIO_PCI_DEVID_NOT_OWNED;
+			fill->dev_owned = 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 +1267,27 @@ 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.dev_owned = 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_DEV_ID;
+			if (fill.dev_owned)
+				hdr.flags |= VFIO_PCI_HOT_RESET_FLAG_DEV_ID_OWNED;
+		}
+	}
 
 reset_info_exit:
 	if (copy_to_user(arg, &hdr, minsz))
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 0552e8dcf0cb..01203215251a 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -650,11 +650,53 @@ 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 devid 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, devid is reported.
+ *	  Flag VFIO_PCI_HOT_RESET_FLAG_DEV_ID is set to indicate this
+ *	  data type.  For a given affected device, it is considered owned by
+ *	  this interface if it meets the following conditions:
+ *	  1) Has a valid devid within the iommufd_ctx of the calling device.
+ *	     Ownership cannot be determined across separate iommufd_ctx and the
+ *	     cdev calling conventions do not support a proof-of-ownership model
+ *	     as provided in the legacy group interface.  In this case a valid
+ *	     devid with value greater than zero is provided in the return
+ *	     structure.
+ *	  2) Does not have a valid devid within the iommufd_ctx of the calling
+ *	     device, but belongs to the same IOMMU group as the calling device
+ *	     or another opened device that has a valid devid within the
+ *	     iommufd_ctx of the calling device.  This provides implicit ownership
+ *	     for devices within the same DMA isolation context.  In this case
+ *	     the invalid devid value of zero is provided in the return structure.
+ *
+ *	  A devid value of -1 is provided in the return structure for devices
+ *	  where ownership is not available.  Such devices prevent the use of
+ *	  VFIO_DEVICE_PCI_HOT_RESET outside of proof-of-ownership calling
+ *	  conventions (ie. via legacy group accessed devices).
+ *	  Flag VFIO_PCI_HOT_RESET_FLAG_DEV_ID_OWNED would be set when all the
+ *	  affected devices are owned by the user.  This flag is available only
+ *	  when VFIO_PCI_HOT_RESET_FLAG_DEV_ID is set, otherwise reserved.
+ *
  * 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	devid;
+#define VFIO_PCI_DEVID_OWNED		0
+#define VFIO_PCI_DEVID_NOT_OWNED	-1
+	};
 	__u16	segment;
 	__u8	bus;
 	__u8	devfn; /* Use PCI_SLOT/PCI_FUNC */
@@ -663,6 +705,8 @@ struct vfio_pci_dependent_device {
 struct vfio_pci_hot_reset_info {
 	__u32	argsz;
 	__u32	flags;
+#define VFIO_PCI_HOT_RESET_FLAG_DEV_ID		(1 << 0)
+#define VFIO_PCI_HOT_RESET_FLAG_DEV_ID_OWNED	(1 << 1)
 	__u32	count;
 	struct vfio_pci_dependent_device	devices[];
 };
-- 
2.34.1