diff options
Diffstat (limited to 'drivers/gpu/drm/xe/xe_pt_walk.c')
-rw-r--r-- | drivers/gpu/drm/xe/xe_pt_walk.c | 160 |
1 files changed, 160 insertions, 0 deletions
diff --git a/drivers/gpu/drm/xe/xe_pt_walk.c b/drivers/gpu/drm/xe/xe_pt_walk.c new file mode 100644 index 0000000000..b8b3d2aea4 --- /dev/null +++ b/drivers/gpu/drm/xe/xe_pt_walk.c @@ -0,0 +1,160 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright © 2022 Intel Corporation + */ +#include "xe_pt_walk.h" + +/** + * DOC: GPU page-table tree walking. + * The utilities in this file are similar to the CPU page-table walk + * utilities in mm/pagewalk.c. The main difference is that we distinguish + * the various levels of a page-table tree with an unsigned integer rather + * than by name. 0 is the lowest level, and page-tables with level 0 can + * not be directories pointing to lower levels, whereas all other levels + * can. The user of the utilities determines the highest level. + * + * Nomenclature: + * Each struct xe_ptw, regardless of level is referred to as a page table, and + * multiple page tables typically form a page table tree with page tables at + * intermediate levels being page directories pointing at page tables at lower + * levels. A shared page table for a given address range is a page-table which + * is neither fully within nor fully outside the address range and that can + * thus be shared by two or more address ranges. + * + * Please keep this code generic so that it can used as a drm-wide page- + * table walker should other drivers find use for it. + */ +static u64 xe_pt_addr_end(u64 addr, u64 end, unsigned int level, + const struct xe_pt_walk *walk) +{ + u64 size = 1ull << walk->shifts[level]; + u64 tmp = round_up(addr + 1, size); + + return min_t(u64, tmp, end); +} + +static bool xe_pt_next(pgoff_t *offset, u64 *addr, u64 next, u64 end, + unsigned int level, const struct xe_pt_walk *walk) +{ + pgoff_t step = 1; + + /* Shared pt walk skips to the last pagetable */ + if (unlikely(walk->shared_pt_mode)) { + unsigned int shift = walk->shifts[level]; + u64 skip_to = round_down(end, 1ull << shift); + + if (skip_to > next) { + step += (skip_to - next) >> shift; + next = skip_to; + } + } + + *addr = next; + *offset += step; + + return next != end; +} + +/** + * xe_pt_walk_range() - Walk a range of a gpu page table tree with callbacks + * for each page-table entry in all levels. + * @parent: The root page table for walk start. + * @level: The root page table level. + * @addr: Virtual address start. + * @end: Virtual address end + 1. + * @walk: Walk info. + * + * Similar to the CPU page-table walker, this is a helper to walk + * a gpu page table and call a provided callback function for each entry. + * + * Return: 0 on success, negative error code on error. The error is + * propagated from the callback and on error the walk is terminated. + */ +int xe_pt_walk_range(struct xe_ptw *parent, unsigned int level, + u64 addr, u64 end, struct xe_pt_walk *walk) +{ + pgoff_t offset = xe_pt_offset(addr, level, walk); + struct xe_ptw **entries = parent->children ? parent->children : NULL; + const struct xe_pt_walk_ops *ops = walk->ops; + enum page_walk_action action; + struct xe_ptw *child; + int err = 0; + u64 next; + + do { + next = xe_pt_addr_end(addr, end, level, walk); + if (walk->shared_pt_mode && xe_pt_covers(addr, next, level, + walk)) + continue; +again: + action = ACTION_SUBTREE; + child = entries ? entries[offset] : NULL; + err = ops->pt_entry(parent, offset, level, addr, next, + &child, &action, walk); + if (err) + break; + + /* Probably not needed yet for gpu pagetable walk. */ + if (unlikely(action == ACTION_AGAIN)) + goto again; + + if (likely(!level || !child || action == ACTION_CONTINUE)) + continue; + + err = xe_pt_walk_range(child, level - 1, addr, next, walk); + + if (!err && ops->pt_post_descend) + err = ops->pt_post_descend(parent, offset, level, addr, + next, &child, &action, walk); + if (err) + break; + + } while (xe_pt_next(&offset, &addr, next, end, level, walk)); + + return err; +} + +/** + * xe_pt_walk_shared() - Walk shared page tables of a page-table tree. + * @parent: Root page table directory. + * @level: Level of the root. + * @addr: Start address. + * @end: Last address + 1. + * @walk: Walk info. + * + * This function is similar to xe_pt_walk_range() but it skips page tables + * that are private to the range. Since the root (or @parent) page table is + * typically also a shared page table this function is different in that it + * calls the pt_entry callback and the post_descend callback also for the + * root. The root can be detected in the callbacks by checking whether + * parent == *child. + * Walking only the shared page tables is common for unbind-type operations + * where the page-table entries for an address range are cleared or detached + * from the main page-table tree. + * + * Return: 0 on success, negative error code on error: If a callback + * returns an error, the walk will be terminated and the error returned by + * this function. + */ +int xe_pt_walk_shared(struct xe_ptw *parent, unsigned int level, + u64 addr, u64 end, struct xe_pt_walk *walk) +{ + const struct xe_pt_walk_ops *ops = walk->ops; + enum page_walk_action action = ACTION_SUBTREE; + struct xe_ptw *child = parent; + int err; + + walk->shared_pt_mode = true; + err = walk->ops->pt_entry(parent, 0, level + 1, addr, end, + &child, &action, walk); + + if (err || action != ACTION_SUBTREE) + return err; + + err = xe_pt_walk_range(parent, level, addr, end, walk); + if (!err && ops->pt_post_descend) { + err = ops->pt_post_descend(parent, 0, level + 1, addr, end, + &child, &action, walk); + } + return err; +} |