[PATCH v3 04/21] KVM: arm64: Introduce helper to retrieve a PTE and its level

Quentin Perret
2021-07-29T13:28:43Z

From: Marc Zyngier <maz@kernel.org>

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>
Signed-off-by: Quentin Perret <qperret@google.com>
---
arch/arm64/include/asm/kvm_pgtable.h | 19 ++++++++++++++
arch/arm64/kvm/hyp/pgtable.c | 39 ++++++++++++++++++++++++++++
2 files changed, 58 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index f004c0115d89..082b9d65f40b 100644
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -432,6 +432,25 @@ 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().
+ * @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 05321f4165e3..78f36bd5df6c 100644
--- 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;
--
2.32.0.432.gabb21c7263-goog