[Intel-gfx] [PATCH v3 02/12] vfio/pci: Only check ownership of opened devices in hot reset

[Eric Auger]

Hi YI,

On 4/1/23 16:44, Yi Liu wrote:
> If the affected device is not opened by any user, it's safe to reset it
> given it's not in use.
>
> Reviewed-by: Kevin Tian <kevin.tian at intel.com>
> Reviewed-by: Jason Gunthorpe <jgg at nvidia.com>
> Tested-by: Yanting Jiang <yanting.jiang at intel.com>
> Signed-off-by: Yi Liu <yi.l.liu at intel.com>
> ---
>  drivers/vfio/pci/vfio_pci_core.c | 14 +++++++++++---
>  include/uapi/linux/vfio.h        |  8 ++++++++
>  2 files changed, 19 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
> index 65bbef562268..5d745c9abf05 100644
> --- a/drivers/vfio/pci/vfio_pci_core.c
> +++ b/drivers/vfio/pci/vfio_pci_core.c
> @@ -2429,10 +2429,18 @@ 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.
> +		 *
> +		 * Resetting an unused device (not opened) is safe, because
> +		 * dev_set->lock is held in hot reset path so this device
> +		 * cannot race being opened by another user simultaneously.
> +		 *
> +		 * Otherwise all opened devices in the dev_set must be
> +		 * contained by the set of groups provided by the user.
>  		 */
> -		if (!vfio_dev_in_groups(cur_vma, groups)) {
> +		if (cur_vma->vdev.open_count &&
> +		    !vfio_dev_in_groups(cur_vma, groups)) {
>  			ret = -EINVAL;
>  			goto err_undo;
>  		}
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 0552e8dcf0cb..f96e5689cffc 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -673,6 +673,14 @@ 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 uses.  Due to the
> + * underlying topology, multiple devices can be affected in the reset
by the reset
> + * while some might be opened by another user.  To avoid interference
s/interference/hot reset failure?
> + * the calling user must ensure all affected devices, if opened, are
> + * owned by itself.
> + *
> + * The ownership is proved by an array of group fds.
> + *
>   * Return: 0 on success, -errno on failure.
>   */
>  struct vfio_pci_hot_reset {
Thanks

Eric