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

Yi Liu
2023-05-13T13:22:03Z

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