On 11/2/23 3:12 AM, Zhenzhong Duan wrote:
> From: Yi Liu <[email protected]>
>
> Add the iommufd backend. The IOMMUFD container class is implemented
> based on the new /dev/iommu user API. This backend obviously depends
> on CONFIG_IOMMUFD.
>
> So far, the iommufd backend doesn't support dirty page sync yet due
> to missing support in the host kernel.
>
> Co-authored-by: Eric Auger <[email protected]>
> Signed-off-by: Eric Auger <[email protected]>
> Signed-off-by: Yi Liu <[email protected]>
> Signed-off-by: Zhenzhong Duan <[email protected]>
> ---
[...]
> +static int iommufd_cdev_attach_container(VFIODevice *vbasedev,
> + VFIOIOMMUFDContainer *container,
> + Error **errp)
> +{
> + int ret, iommufd = vbasedev->iommufd->fd;
> + VFIOIOASHwpt *hwpt;
> + uint32_t hwpt_id;
> + Error *err = NULL;
> +
> + /* try to attach to an existing hwpt in this container */
> + QLIST_FOREACH(hwpt, &container->hwpt_list, next) {
> + ret = iommufd_cdev_attach_hwpt(vbasedev, hwpt->hwpt_id, &err);
> + if (ret) {
> + const char *msg = error_get_pretty(err);
> +
> + trace_iommufd_cdev_fail_attach_existing_hwpt(msg);
> + error_free(err);
> + err = NULL;
> + } else {
> + goto found_hwpt;
> + }
> + }
> +
> + ret = iommufd_backend_alloc_hwpt(iommufd, vbasedev->devid,
> + container->ioas_id, &hwpt_id);
> +
> + if (ret) {
> + error_setg_errno(errp, errno, "error alloc shadow hwpt");
> + return ret;
> + }
The above alloc_hwpt fails for mdevs (at least, it fails for me attempting to
use iommufd backend with vfio-ccw and vfio-ap on s390). The ioctl is failing
in the kernel because it can't find an IOMMUFD_OBJ_DEVICE.
AFAIU that's because the mdevs are meant to instead use kernel access via
vfio_iommufd_emulated_attach_ioas, not hwpt. That's how mdevs behave when
looking at the kernel vfio compat container.
As a test, I was able to get vfio-ccw and vfio-ap working using the iommufd
backend by just skipping this alloc_hwpt above and instead passing
container->ioas_id into the iommufd_cdev_attach_hwpt below. That triggers the
vfio_iommufd_emulated_attach_ioas call in the kernel.
> +
> + /* Attach cdev to a new allocated hwpt within iommufd */
> + ret = iommufd_cdev_attach_hwpt(vbasedev, hwpt_id, errp);
> + if (ret) {
> + iommufd_backend_free_id(iommufd, hwpt_id);
> + return ret;
> + }
> +
> + hwpt = iommufd_container_get_hwpt(container, hwpt_id);
> +found_hwpt:
> + QLIST_INSERT_HEAD(&hwpt->device_list, vbasedev, next);
> + vbasedev->hwpt = hwpt;
> +
> + trace_iommufd_cdev_attach_container(iommufd, vbasedev->name,
> vbasedev->fd,
> + container->ioas_id, hwpt->hwpt_id);
> + return ret;
> +}
