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 goal_gfn.
27 void tdp_iter_start(struct tdp_iter *iter, u64 *root_pt, int root_level,
28 int min_level, gfn_t goal_gfn)
30 WARN_ON(root_level < 1);
31 WARN_ON(root_level > PT64_ROOT_MAX_LEVEL);
33 iter->goal_gfn = goal_gfn;
34 iter->root_level = root_level;
35 iter->min_level = min_level;
36 iter->level = root_level;
37 iter->pt_path[iter->level - 1] = root_pt;
39 iter->gfn = round_gfn_for_level(iter->goal_gfn, iter->level);
40 tdp_iter_refresh_sptep(iter);
46 * Given an SPTE and its level, returns a pointer containing the host virtual
47 * address of the child page table referenced by the SPTE. Returns null if
48 * there is no such entry.
50 u64 *spte_to_child_pt(u64 spte, int level)
53 * There's no child entry if this entry isn't present or is a
56 if (!is_shadow_present_pte(spte) || is_last_spte(spte, level))
59 return __va(spte_to_pfn(spte) << PAGE_SHIFT);
63 * Steps down one level in the paging structure towards the goal GFN. Returns
64 * true if the iterator was able to step down a level, false otherwise.
66 static bool try_step_down(struct tdp_iter *iter)
70 if (iter->level == iter->min_level)
74 * Reread the SPTE before stepping down to avoid traversing into page
75 * tables that are no longer linked from this entry.
77 iter->old_spte = READ_ONCE(*iter->sptep);
79 child_pt = spte_to_child_pt(iter->old_spte, iter->level);
84 iter->pt_path[iter->level - 1] = child_pt;
85 iter->gfn = round_gfn_for_level(iter->goal_gfn, iter->level);
86 tdp_iter_refresh_sptep(iter);
92 * Steps to the next entry in the current page table, at the current page table
93 * level. The next entry could point to a page backing guest memory or another
94 * page table, or it could be non-present. Returns true if the iterator was
95 * able to step to the next entry in the page table, false if the iterator was
96 * already at the end of the current page table.
98 static bool try_step_side(struct tdp_iter *iter)
101 * Check if the iterator is already at the end of the current page
104 if (SHADOW_PT_INDEX(iter->gfn << PAGE_SHIFT, iter->level) ==
105 (PT64_ENT_PER_PAGE - 1))
108 iter->gfn += KVM_PAGES_PER_HPAGE(iter->level);
109 iter->goal_gfn = iter->gfn;
111 iter->old_spte = READ_ONCE(*iter->sptep);
117 * Tries to traverse back up a level in the paging structure so that the walk
118 * can continue from the next entry in the parent page table. Returns true on a
119 * successful step up, false if already in the root page.
121 static bool try_step_up(struct tdp_iter *iter)
123 if (iter->level == iter->root_level)
127 iter->gfn = round_gfn_for_level(iter->gfn, iter->level);
128 tdp_iter_refresh_sptep(iter);
134 * Step to the next SPTE in a pre-order traversal of the paging structure.
135 * To get to the next SPTE, the iterator either steps down towards the goal
136 * GFN, if at a present, non-last-level SPTE, or over to a SPTE mapping a
139 * The basic algorithm is as follows:
140 * 1. If the current SPTE is a non-last-level SPTE, step down into the page
141 * table it points to.
142 * 2. If the iterator cannot step down, it will try to step to the next SPTE
143 * in the current page of the paging structure.
144 * 3. If the iterator cannot step to the next entry in the current page, it will
145 * try to step up to the parent paging structure page. In this case, that
146 * SPTE will have already been visited, and so the iterator must also step
149 void tdp_iter_next(struct tdp_iter *iter)
151 if (try_step_down(iter))
155 if (try_step_side(iter))
157 } while (try_step_up(iter));
162 * Restart the walk over the paging structure from the root, starting from the
163 * highest gfn the iterator had previously reached. Assumes that the entire
164 * paging structure, except the root page, may have been completely torn down
167 void tdp_iter_refresh_walk(struct tdp_iter *iter)
169 gfn_t goal_gfn = iter->goal_gfn;
171 if (iter->gfn > goal_gfn)
172 goal_gfn = iter->gfn;
174 tdp_iter_start(iter, iter->pt_path[iter->root_level - 1],
175 iter->root_level, iter->min_level, goal_gfn);
178 u64 *tdp_iter_root_pt(struct tdp_iter *iter)
180 return iter->pt_path[iter->root_level - 1];