1 // SPDX-License-Identifier: GPL-2.0
2 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
4 #include "mmu_internal.h"
9 * Recalculates the pointer to the SPTE for the current GFN and level and
12 static void tdp_iter_refresh_sptep(struct tdp_iter *iter)
14 iter->sptep = iter->pt_path[iter->level - 1] +
15 SPTE_INDEX(iter->gfn << PAGE_SHIFT, iter->level);
16 iter->old_spte = kvm_tdp_mmu_read_spte(iter->sptep);
20 * Return the TDP iterator to the root PT and allow it to continue its
21 * traversal over the paging structure from there.
23 void tdp_iter_restart(struct tdp_iter *iter)
25 iter->yielded = false;
26 iter->yielded_gfn = iter->next_last_level_gfn;
27 iter->level = iter->root_level;
29 iter->gfn = gfn_round_for_level(iter->next_last_level_gfn, iter->level);
30 tdp_iter_refresh_sptep(iter);
36 * Sets a TDP iterator to walk a pre-order traversal of the paging structure
37 * rooted at root_pt, starting with the walk to translate next_last_level_gfn.
39 void tdp_iter_start(struct tdp_iter *iter, struct kvm_mmu_page *root,
40 int min_level, gfn_t next_last_level_gfn)
42 if (WARN_ON_ONCE(!root || (root->role.level < 1) ||
43 (root->role.level > PT64_ROOT_MAX_LEVEL))) {
48 iter->next_last_level_gfn = next_last_level_gfn;
49 iter->root_level = root->role.level;
50 iter->min_level = min_level;
51 iter->pt_path[iter->root_level - 1] = (tdp_ptep_t)root->spt;
52 iter->as_id = kvm_mmu_page_as_id(root);
54 tdp_iter_restart(iter);
58 * Given an SPTE and its level, returns a pointer containing the host virtual
59 * address of the child page table referenced by the SPTE. Returns null if
60 * there is no such entry.
62 tdp_ptep_t spte_to_child_pt(u64 spte, int level)
65 * There's no child entry if this entry isn't present or is a
68 if (!is_shadow_present_pte(spte) || is_last_spte(spte, level))
71 return (tdp_ptep_t)__va(spte_to_pfn(spte) << PAGE_SHIFT);
75 * Steps down one level in the paging structure towards the goal GFN. Returns
76 * true if the iterator was able to step down a level, false otherwise.
78 static bool try_step_down(struct tdp_iter *iter)
82 if (iter->level == iter->min_level)
86 * Reread the SPTE before stepping down to avoid traversing into page
87 * tables that are no longer linked from this entry.
89 iter->old_spte = kvm_tdp_mmu_read_spte(iter->sptep);
91 child_pt = spte_to_child_pt(iter->old_spte, iter->level);
96 iter->pt_path[iter->level - 1] = child_pt;
97 iter->gfn = gfn_round_for_level(iter->next_last_level_gfn, iter->level);
98 tdp_iter_refresh_sptep(iter);
104 * Steps to the next entry in the current page table, at the current page table
105 * level. The next entry could point to a page backing guest memory or another
106 * page table, or it could be non-present. Returns true if the iterator was
107 * able to step to the next entry in the page table, false if the iterator was
108 * already at the end of the current page table.
110 static bool try_step_side(struct tdp_iter *iter)
113 * Check if the iterator is already at the end of the current page
116 if (SPTE_INDEX(iter->gfn << PAGE_SHIFT, iter->level) ==
117 (SPTE_ENT_PER_PAGE - 1))
120 iter->gfn += KVM_PAGES_PER_HPAGE(iter->level);
121 iter->next_last_level_gfn = iter->gfn;
123 iter->old_spte = kvm_tdp_mmu_read_spte(iter->sptep);
129 * Tries to traverse back up a level in the paging structure so that the walk
130 * can continue from the next entry in the parent page table. Returns true on a
131 * successful step up, false if already in the root page.
133 static bool try_step_up(struct tdp_iter *iter)
135 if (iter->level == iter->root_level)
139 iter->gfn = gfn_round_for_level(iter->gfn, iter->level);
140 tdp_iter_refresh_sptep(iter);
146 * Step to the next SPTE in a pre-order traversal of the paging structure.
147 * To get to the next SPTE, the iterator either steps down towards the goal
148 * GFN, if at a present, non-last-level SPTE, or over to a SPTE mapping a
151 * The basic algorithm is as follows:
152 * 1. If the current SPTE is a non-last-level SPTE, step down into the page
153 * table it points to.
154 * 2. If the iterator cannot step down, it will try to step to the next SPTE
155 * in the current page of the paging structure.
156 * 3. If the iterator cannot step to the next entry in the current page, it will
157 * try to step up to the parent paging structure page. In this case, that
158 * SPTE will have already been visited, and so the iterator must also step
161 void tdp_iter_next(struct tdp_iter *iter)
164 tdp_iter_restart(iter);
168 if (try_step_down(iter))
172 if (try_step_side(iter))
174 } while (try_step_up(iter));