RE: [PATCH v5 09/19] vfio/pci: Allow passing zero-length fd array in VFIO_DEVICE_PCI_HOT_RESET

Tian, Kevin
2023-03-06T08:23:36Z

> From: Tian, Kevin <kevin.tian@intel.com>
> Sent: Monday, March 6, 2023 4:17 PM
>
> > From: Liu, Yi L <yi.l.liu@intel.com>
> > Sent: Sunday, March 5, 2023 10:49 PM
> >
> >
> > How about falling back to prior solution. Allow userspace to pass a set
> > of device fd, and the kernel just checks the opened devices in the dev_set,
> > all the opened devices should be included in the device fd set. If not all
> > of them are included, fail it.
> >
>
> looks this is a cleaner approach.
>
> if a device is not opened we know it's safe to reset.
>
> If a device is opened then it must be opened by the calling process to be
> reset.
>
> from this angle we don't need to bother with noiommu vs. iommufd
> when iommufd is not always available.

btw there is one thing to be fixed in your next version.

noiommu shouldn't be enabled on a device which always has a iommu group.

We need a check on iommu_group in following place:

+ /* iommufd < 0 means noiommu mode */
+ if (bind.iommufd < 0) {
+ if (!capable(CAP_SYS_RAWIO)) {
+ ret = -EPERM;
+ goto out_unlock;
+ }
+ df->noiommu = true;