[RFC,08/17] KVM: arm64: Spin off helper for initializing table pte

Commit Message

Oliver Upton April 15, 2022, 9:58 p.m. UTC

With parallel table walks there is no guarantee that KVM reads back the
same pte that was written. Spin off a helper that creates a pte value,
thereby allowing the visitor callback to return the next table without
reading the ptep again.

Signed-off-by: Oliver Upton <[e-mail]>
---
 arch/arm64/kvm/hyp/pgtable.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

Patch

diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index ff6f14755d0c..ffdfd5ee9642 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -167,14 +167,23 @@  static void kvm_clear_pte(kvm_pte_t *ptep)
 	WRITE_ONCE(*ptep, 0);
 }
 
-static void kvm_set_table_pte(kvm_pte_t *ptep, kvm_pte_t *childp,
-			      struct kvm_pgtable_mm_ops *mm_ops)
+static kvm_pte_t kvm_init_table_pte(kvm_pte_t *childp, struct kvm_pgtable_mm_ops *mm_ops)
 {
-	kvm_pte_t old = *ptep, pte = kvm_phys_to_pte(mm_ops->virt_to_phys(childp));
+	kvm_pte_t pte = kvm_phys_to_pte(mm_ops->virt_to_phys(childp));
 
 	pte |= FIELD_PREP(KVM_PTE_TYPE, KVM_PTE_TYPE_TABLE);
 	pte |= KVM_PTE_VALID;
 
+	return pte;
+}
+
+static void kvm_set_table_pte(kvm_pte_t *ptep, kvm_pte_t *childp,
+			      struct kvm_pgtable_mm_ops *mm_ops)
+{
+	kvm_pte_t pte, old = *ptep;
+
+	pte = kvm_init_table_pte(childp, mm_ops);
+
 	WARN_ON(kvm_pte_valid(old));
 	smp_store_release(ptep, pte);
 }
@@ -931,7 +940,7 @@  static int stage2_map_walk_leaf(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
 				kvm_pte_t *old, struct stage2_map_data *data, bool shared)
 {
 	struct kvm_pgtable_mm_ops *mm_ops = data->mm_ops;
-	kvm_pte_t *childp;
+	kvm_pte_t *childp, pte;
 	int ret;
 
 	if (data->anchor) {
@@ -969,9 +978,9 @@  static int stage2_map_walk_leaf(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
 	 * a table. Accesses beyond 'end' that fall within the new table
 	 * will be mapped lazily.
 	 */
-	kvm_set_table_pte(ptep, childp, mm_ops);
-	mm_ops->get_page(ptep);
-	*old = *ptep;
+	pte = kvm_init_table_pte(childp, mm_ops);
+	stage2_make_pte(ptep, pte, data->mm_ops);
+	*old = pte;
 	return 0;
 }