Re: [PATCH v6 06/14] iommufd/viommu: Add iommufd_viommu_get_vdev_id helper

On Tue, Feb 18, 2025 at 11:31:54AM -0400, Jason Gunthorpe wrote:

On Fri, Jan 24, 2025 at 04:30:35PM -0800, Nicolin Chen wrote:

quoted

This is a reverse search v.s. iommufd_viommu_find_dev, as drivers may want
to convert a struct device pointer (physical) to its virtual device ID for
an event injection to the user space VM.

Again, this avoids exposing more core structures to the drivers, than the
iommufd_viommu alone.

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Nicolin Chen <redacted>
---
 include/linux/iommufd.h        |  9 +++++++++
 drivers/iommu/iommufd/driver.c | 24 ++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>

quoted

+	xa_lock(&viommu->vdevs);
+	xa_for_each(&viommu->vdevs, index, vdev) {
+		if (vdev->dev == dev) {
+			*vdev_id = (unsigned long)vdev->id;

I don't think we need this cast

The left side is ulong for xarray index, while the right side is
__aligned_u64 for uAPI. Could there be a gcc warning when somebody
builds the kernel having a BITS_PER_LONG=32?

iommufd_vdevice_alloc_ioctl() does test vdev->id against ULONG_MAX
though..

Thanks
Nicolin