1 // SPDX-License-Identifier: GPL-2.0
3 #include "mmu_internal.h"
8 * Recalculates the pointer to the SPTE for the current GFN and level and
11 static void tdp_iter_refresh_sptep(struct tdp_iter *iter)
13 iter->sptep = iter->pt_path[iter->level - 1] +
14 SHADOW_PT_INDEX(iter->gfn << PAGE_SHIFT, iter->level);
15 iter->old_spte = READ_ONCE(*iter->sptep);
18 static gfn_t round_gfn_for_level(gfn_t gfn, int level)
20 return gfn & -KVM_PAGES_PER_HPAGE(level);
24 * Sets a TDP iterator to walk a pre-order traversal of the paging structure
25 * rooted at root_pt, starting with the walk to translate next_last_level_gfn.
27 void tdp_iter_start(struct tdp_iter *iter, u64 *root_pt, int root_level,
28 int min_level, gfn_t next_last_level_gfn)
30 WARN_ON(root_level < 1);
31 WARN_ON(root_level > PT64_ROOT_MAX_LEVEL);
33 iter->next_last_level_gfn = next_last_level_gfn;
34 iter->yielded_gfn = iter->next_last_level_gfn;
35 iter->root_level = root_level;
36 iter->min_level = min_level;
37 iter->level = root_level;
38 iter->pt_path[iter->level - 1] = root_pt;
40 iter->gfn = round_gfn_for_level(iter->next_last_level_gfn, iter->level);
41 tdp_iter_refresh_sptep(iter);
47 * Given an SPTE and its level, returns a pointer containing the host virtual
48 * address of the child page table referenced by the SPTE. Returns null if
49 * there is no such entry.
51 u64 *spte_to_child_pt(u64 spte, int level)
54 * There's no child entry if this entry isn't present or is a
57 if (!is_shadow_present_pte(spte) || is_last_spte(spte, level))
60 return __va(spte_to_pfn(spte) << PAGE_SHIFT);
64 * Steps down one level in the paging structure towards the goal GFN. Returns
65 * true if the iterator was able to step down a level, false otherwise.
67 static bool try_step_down(struct tdp_iter *iter)
71 if (iter->level == iter->min_level)
75 * Reread the SPTE before stepping down to avoid traversing into page
76 * tables that are no longer linked from this entry.
78 iter->old_spte = READ_ONCE(*iter->sptep);
80 child_pt = spte_to_child_pt(iter->old_spte, iter->level);
85 iter->pt_path[iter->level - 1] = child_pt;
86 iter->gfn = round_gfn_for_level(iter->next_last_level_gfn, iter->level);
87 tdp_iter_refresh_sptep(iter);
93 * Steps to the next entry in the current page table, at the current page table
94 * level. The next entry could point to a page backing guest memory or another
95 * page table, or it could be non-present. Returns true if the iterator was
96 * able to step to the next entry in the page table, false if the iterator was
97 * already at the end of the current page table.
99 static bool try_step_side(struct tdp_iter *iter)
102 * Check if the iterator is already at the end of the current page
105 if (SHADOW_PT_INDEX(iter->gfn << PAGE_SHIFT, iter->level) ==
106 (PT64_ENT_PER_PAGE - 1))
109 iter->gfn += KVM_PAGES_PER_HPAGE(iter->level);
110 iter->next_last_level_gfn = iter->gfn;
112 iter->old_spte = READ_ONCE(*iter->sptep);
118 * Tries to traverse back up a level in the paging structure so that the walk
119 * can continue from the next entry in the parent page table. Returns true on a
120 * successful step up, false if already in the root page.
122 static bool try_step_up(struct tdp_iter *iter)
124 if (iter->level == iter->root_level)
128 iter->gfn = round_gfn_for_level(iter->gfn, iter->level);
129 tdp_iter_refresh_sptep(iter);
135 * Step to the next SPTE in a pre-order traversal of the paging structure.
136 * To get to the next SPTE, the iterator either steps down towards the goal
137 * GFN, if at a present, non-last-level SPTE, or over to a SPTE mapping a
140 * The basic algorithm is as follows:
141 * 1. If the current SPTE is a non-last-level SPTE, step down into the page
142 * table it points to.
143 * 2. If the iterator cannot step down, it will try to step to the next SPTE
144 * in the current page of the paging structure.
145 * 3. If the iterator cannot step to the next entry in the current page, it will
146 * try to step up to the parent paging structure page. In this case, that
147 * SPTE will have already been visited, and so the iterator must also step
150 void tdp_iter_next(struct tdp_iter *iter)
152 if (try_step_down(iter))
156 if (try_step_side(iter))
158 } while (try_step_up(iter));
162 u64 *tdp_iter_root_pt(struct tdp_iter *iter)
164 return iter->pt_path[iter->root_level - 1];