On Thu, Aug 15, 2024 at 04:08:48PM -0300, Jason Gunthorpe wrote:
On Wed, Aug 07, 2024 at 01:10:46PM -0700, Nicolin Chen wrote:
+int iommufd_viommu_set_vdev_id(struct iommufd_ucmd *ucmd) +{
- struct iommu_viommu_set_vdev_id *cmd = ucmd->cmd;
- struct iommufd_hwpt_nested *hwpt_nested;
- struct iommufd_vdev_id *vdev_id, *curr;
- struct iommufd_hw_pagetable *hwpt;
- struct iommufd_viommu *viommu;
- struct iommufd_device *idev;
- int rc = 0;
- if (cmd->vdev_id > ULONG_MAX)
return -EINVAL;- idev = iommufd_get_device(ucmd, cmd->dev_id);
- if (IS_ERR(idev))
return PTR_ERR(idev);- hwpt = idev->igroup->hwpt;
- if (hwpt == NULL || hwpt->obj.type != IOMMUFD_OBJ_HWPT_NESTED) {
rc = -EINVAL;goto out_put_idev;- }
- hwpt_nested = container_of(hwpt, struct iommufd_hwpt_nested, common);
This doesn't seem like a necessary check, the attached hwpt can change after this is established, so this can't be an invariant we enforce.
If you want to do 1:1 then somehow directly check if the idev is already linked to a viommu.
But idev can't link to a viommu without a proxy hwpt_nested? Even the stage-2 only configuration should have an identity hwpt_nested right?
+static struct device * +iommufd_viommu_find_device(struct iommufd_viommu *viommu, u64 id) +{
- struct iommufd_vdev_id *vdev_id;
- xa_lock(&viommu->vdev_ids);
- vdev_id = xa_load(&viommu->vdev_ids, (unsigned long)id);
- xa_unlock(&viommu->vdev_ids);
This lock doesn't do anything
- if (!vdev_id || vdev_id->vdev_id != id)
return NULL;And this is unlocked
- return vdev_id->dev;
+}
This isn't good.. We can't return the struct device pointer here as there is no locking for it anymore. We can't even know it is still probed to VFIO anymore.
It has to work by having the iommu driver directly access the xarray and the entirely under the spinlock the iommu driver can translate the vSID to the pSID and the let go and push the invalidation to HW. No races.
Maybe the iommufd_viommu_invalidate ioctl handler should hold that xa_lock around the viommu->ops->cache_invalidate, and then add lock assert in iommufd_viommu_find_device?
+int iommufd_viommu_unset_vdev_id(struct iommufd_ucmd *ucmd) +{
- struct iommu_viommu_unset_vdev_id *cmd = ucmd->cmd;
- struct iommufd_vdev_id *vdev_id;
- struct iommufd_viommu *viommu;
- struct iommufd_device *idev;
- int rc = 0;
- idev = iommufd_get_device(ucmd, cmd->dev_id);
- if (IS_ERR(idev))
return PTR_ERR(idev);- viommu = iommufd_get_viommu(ucmd, cmd->viommu_id);
- if (IS_ERR(viommu)) {
rc = PTR_ERR(viommu);goto out_put_idev;- }
- if (idev->dev != iommufd_viommu_find_device(viommu, cmd->vdev_id)) {
Swap the order around != to be more kernely
Ack.
rc = -EINVAL;goto out_put_viommu;- }
- vdev_id = xa_erase(&viommu->vdev_ids, cmd->vdev_id);
And this whole thing needs to be done under the xa_lock too.
xa_lock(&viommu->vdev_ids); vdev_id = xa_load(&viommu->vdev_ids, cmd->vdev_id); if (!vdev_id || vdev_id->vdev_id != cmd->vdev_id (????) || vdev_id->dev != idev->dev) err __xa_erase(&viommu->vdev_ids, cmd->vdev_id); xa_unlock((&viommu->vdev_ids);
I've changed to xa_cmpxchg() in my local tree. Would it be simpler?
Thanks Nicolin