KVM: arm64: Introduce helper to retrieve a PTE and its level

It is becoming a common need to fetch the PTE for a given address
together with its level. Add such a helper.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Quentin Perret <qperret@google.com>
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Link: https://lore.kernel.org/r/20210726153552.1535838-2-maz@kernel.org

diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index f004c01..e42b55b 100644 (file)
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -432,6 +432,26 @@ int kvm_pgtable_stage2_flush(struct kvm_pgtable *pgt, u64 addr, u64 size);
 int kvm_pgtable_walk(struct kvm_pgtable *pgt, u64 addr, u64 size,
                     struct kvm_pgtable_walker *walker);
 
+/**
+ * kvm_pgtable_get_leaf() - Walk a page-table and retrieve the leaf entry
+ *                         with its level.
+ * @pgt:       Page-table structure initialised by kvm_pgtable_*_init()
+ *             or a similar initialiser.
+ * @addr:      Input address for the start of the walk.
+ * @ptep:      Pointer to storage for the retrieved PTE.
+ * @level:     Pointer to storage for the level of the retrieved PTE.
+ *
+ * The offset of @addr within a page is ignored.
+ *
+ * The walker will walk the page-table entries corresponding to the input
+ * address specified, retrieving the leaf corresponding to this address.
+ * Invalid entries are treated as leaf entries.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+int kvm_pgtable_get_leaf(struct kvm_pgtable *pgt, u64 addr,
+                        kvm_pte_t *ptep, u32 *level);
+
 /**
  * kvm_pgtable_stage2_find_range() - Find a range of Intermediate Physical
  *                                  Addresses with compatible permission

diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index 05321f4..78f36bd 100644 (file)
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -326,6 +326,45 @@ int kvm_pgtable_walk(struct kvm_pgtable *pgt, u64 addr, u64 size,
        return _kvm_pgtable_walk(&walk_data);
 }
 
+struct leaf_walk_data {
+       kvm_pte_t       pte;
+       u32             level;
+};
+
+static int leaf_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
+                      enum kvm_pgtable_walk_flags flag, void * const arg)
+{
+       struct leaf_walk_data *data = arg;
+
+       data->pte   = *ptep;
+       data->level = level;
+
+       return 0;
+}
+
+int kvm_pgtable_get_leaf(struct kvm_pgtable *pgt, u64 addr,
+                        kvm_pte_t *ptep, u32 *level)
+{
+       struct leaf_walk_data data;
+       struct kvm_pgtable_walker walker = {
+               .cb     = leaf_walker,
+               .flags  = KVM_PGTABLE_WALK_LEAF,
+               .arg    = &data,
+       };
+       int ret;
+
+       ret = kvm_pgtable_walk(pgt, ALIGN_DOWN(addr, PAGE_SIZE),
+                              PAGE_SIZE, &walker);
+       if (!ret) {
+               if (ptep)
+                       *ptep  = data.pte;
+               if (level)
+                       *level = data.level;
+       }
+
+       return ret;
+}
+
 struct hyp_map_data {
        u64                             phys;
        kvm_pte_t                       attr;