Re: [Intel-gfx] [PATCH v7 8/9] vfio/pci: Extend VFIO_DEVICE_GET_PCI_HOT_RESET_INFO for vfio device cdev

Jason Gunthorpe
2023-06-13T18:23:11Z

On Fri, Jun 02, 2023 at 05:15:14AM -0700, Yi Liu wrote:
> This allows VFIO_DEVICE_GET_PCI_HOT_RESET_INFO ioctl use the iommufd_ctx
> of the cdev device to check the ownership of the other affected devices.
>
> When VFIO_DEVICE_GET_PCI_HOT_RESET_INFO is called on an IOMMUFD managed
> device, the new flag VFIO_PCI_HOT_RESET_FLAG_DEV_ID is reported to indicate
> the values returned are IOMMUFD devids rather than group IDs as used when
> accessing vfio devices through the conventional vfio group interface.
> Additionally the flag VFIO_PCI_HOT_RESET_FLAG_DEV_ID_OWNED will be reported
> in this mode if all of the devices affected by the hot-reset are owned by
> either virtue of being directly bound to the same iommufd context as the
> calling device, or implicitly owned via a shared IOMMU group.
>
> 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/iommufd.c | 49 +++++++++++++++++++++++++++++++
> drivers/vfio/pci/vfio_pci_core.c | 47 +++++++++++++++++++++++++-----
> include/linux/vfio.h | 16 ++++++++++
> include/uapi/linux/vfio.h | 50 +++++++++++++++++++++++++++++++-
> 4 files changed, 154 insertions(+), 8 deletions(-)

This could use some more fiddling, like we could copy each
vfio_pci_dependent_device to user memory inside the loop instead of
allocating an array.

Add another patch with something like this in it:

diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index b0eadafcbcf502..516e0fda74bec9 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -775,19 +775,23 @@ static int vfio_pci_count_devs(struct pci_dev *pdev, void *data)
}

struct vfio_pci_fill_info {
- int max;
- int cur;
- struct vfio_pci_dependent_device *devices;
+ struct vfio_pci_dependent_device __user *devices;
+ struct vfio_pci_dependent_device __user *devices_end;
struct vfio_device *vdev;
u32 flags;
};

static int vfio_pci_fill_devs(struct pci_dev *pdev, void *data)
{
+ struct vfio_pci_dependent_device info = {
+ .segment = pci_domain_nr(pdev->bus),
+ .bus = pdev->bus->number,
+ .devfn = pdev->devfn,
+ };
struct vfio_pci_fill_info *fill = data;

- if (fill->cur == fill->max)
- return -EAGAIN; /* Something changed, try again */
+ if (fill->devices_end >= fill->devices)
+ return -ENOSPC;

if (fill->flags & VFIO_PCI_HOT_RESET_FLAG_DEV_ID) {
struct iommufd_ctx *iommufd = vfio_iommufd_device_ictx(fill->vdev);
@@ -800,12 +804,12 @@ static int vfio_pci_fill_devs(struct pci_dev *pdev, void *data)
*/
vdev = vfio_find_device_in_devset(dev_set, &pdev->dev);
if (!vdev)
- fill->devices[fill->cur].devid = VFIO_PCI_DEVID_NOT_OWNED;
+ info.devid = VFIO_PCI_DEVID_NOT_OWNED;
else
- fill->devices[fill->cur].devid =
- vfio_iommufd_device_hot_reset_devid(vdev, iommufd);
+ info.devid = vfio_iommufd_device_hot_reset_devid(
+ vdev, iommufd);
/* If devid is VFIO_PCI_DEVID_NOT_OWNED, clear owned flag. */
- if (fill->devices[fill->cur].devid == VFIO_PCI_DEVID_NOT_OWNED)
+ if (info.devid == VFIO_PCI_DEVID_NOT_OWNED)
fill->flags &= ~VFIO_PCI_HOT_RESET_FLAG_DEV_ID_OWNED;
} else {
struct iommu_group *iommu_group;
@@ -814,13 +818,13 @@ 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);
+ info.group_id = iommu_group_id(iommu_group);
iommu_group_put(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;
- fill->cur++;
+
+ if (copy_to_user(fill->devices, &info, sizeof(info)))
+ return -EFAULT;
+ fill->devices++;
return 0;
}

@@ -1212,8 +1216,7 @@ static int vfio_pci_ioctl_get_pci_hot_reset_info(
unsigned long minsz =
offsetofend(struct vfio_pci_hot_reset_info, count);
struct vfio_pci_hot_reset_info hdr;
- struct vfio_pci_fill_info fill = { 0 };
- struct vfio_pci_dependent_device *devices = NULL;
+ struct vfio_pci_fill_info fill = {};
bool slot = false;
int ret = 0;

@@ -1231,29 +1234,9 @@ static int vfio_pci_ioctl_get_pci_hot_reset_info(
else if (pci_probe_reset_bus(vdev->pdev->bus))
return -ENODEV;

- /* How many devices are affected? */
- ret = vfio_pci_for_each_slot_or_bus(vdev->pdev, vfio_pci_count_devs,
- &fill.max, slot);
- if (ret)
- return ret;
-
- WARN_ON(!fill.max); /* Should always be at least one */
-
- /*
- * If there's enough space, fill it now, otherwise return -ENOSPC and
- * the number of devices affected.
- */
- if (hdr.argsz < sizeof(hdr) + (fill.max * sizeof(*devices))) {
- ret = -ENOSPC;
- hdr.count = fill.max;
- goto reset_info_exit;
- }
-
- devices = kcalloc(fill.max, sizeof(*devices), GFP_KERNEL);
- if (!devices)
- return -ENOMEM;
-
- fill.devices = devices;
+ fill.devices = arg->devices;
+ fill.devices_end = arg->devices +
+ (hdr.argsz - sizeof(hdr)) / sizeof(arg->devices[0]);
fill.vdev = &vdev->vdev;

if (vfio_device_cdev_opened(&vdev->vdev))
@@ -1264,29 +1247,14 @@ static int vfio_pci_ioctl_get_pci_hot_reset_info(
ret = vfio_pci_for_each_slot_or_bus(vdev->pdev, vfio_pci_fill_devs,
&fill, slot);
mutex_unlock(&vdev->vdev.dev_set->lock);
+ if (ret)
+ return ret;

- /*
- * 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) {
- hdr.count = fill.cur;
- hdr.flags = fill.flags;
- }
-
-reset_info_exit:
+ hdr.count = fill.devices - arg->devices;
+ hdr.flags = fill.flags;
if (copy_to_user(arg, &hdr, minsz))
ret = -EFAULT;
-
- if (!ret) {
- if (copy_to_user(&arg->devices, devices,
- hdr.count * sizeof(*devices)))
- ret = -EFAULT;
- }
-
- kfree(devices);
- return ret;
+ return 0;
}

static int