On Tue, May 16, 2023 at 11:00:16AM +0800, Baolu Lu wrote:
On 5/15/23 10:00 PM, Jason Gunthorpe wrote:
The devices list was used as a simple way to avoid having per-group information. Now that this seems to be unavoidable, just commit to per-group information fully and remove the devices list from the HWPT.
The iommufd_group stores the currently assigned HWPT for the entire group and we can manage the per-device attach/detach with a list in the iommufd_group.
I am preparing the patches to route I/O page faults to user space through iommufd. The iommufd page fault handler knows the hwpt and the device pointer, but it needs to convert the device pointer into its iommufd object id and pass the id to user space.
It's fine that we remove the hwpt->devices here, but perhaps I need to add the context pointer in ioas later,
struct iommufd_ioas { struct io_pagetable iopt; struct mutex mutex; struct list_head hwpt_list;
struct iommufd_ctx *ictx;};
and, use below helper to look up the device id.
+u32 iommufd_get_device_id(struct iommufd_ctx *ictx, struct device *dev) +{
struct iommu_group *group = iommu_group_get(dev);u32 dev_id = IOMMUFD_INVALID_OBJ_ID;struct iommufd_group *igroup;struct iommufd_device *cur;unsigned int id;if (!group)return IOMMUFD_INVALID_OBJ_ID;id = iommu_group_id(group);xa_lock(&ictx->groups);igroup = xa_load(&ictx->groups, id);if (!iommufd_group_try_get(igroup, group)) {xa_unlock(&ictx->groups);iommu_group_put(group);return IOMMUFD_INVALID_OBJ_ID;}xa_unlock(&ictx->groups);mutex_lock(&igroup->lock);list_for_each_entry(cur, &igroup->device_list, group_item) {if (cur->dev == dev) {dev_id = cur->obj.id;break;}}
I dislike how slow this is on something resembling a fastish path :\
Maybe we should stash something in the dev_iommu instead?
Or can the PRI stuff provide a cookie per-device?
But it will work like this
dev_id = iommufd_get_device_id(hwpt->ioas->ictx, dev);
Where did the hwpt come from?
Jason