2 files changed, 26 insertions, 11 deletions
diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index 52ab38db04c7..8886d43cfb11 100644
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -157,6 +157,11 @@ void kvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt);
  * If device attributes are not explicitly requested in @prot, then the
  * mapping will be normal, cacheable.
  *
+ * Note that the update of a valid leaf PTE in this function will be aborted,
+ * if it's trying to recreate the exact same mapping or only change the access
+ * permissions. Instead, the vCPU will exit one more time from guest if still
+ * needed and then go through the path of relaxing permissions.
+ *
  * Note that this function will both coalesce existing table entries and split
  * existing block mappings, relying on page-faults to fault back areas outside
  * of the new mapping lazily.
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index a11ac874bc2a..4d177ce1d536 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -45,6 +45,10 @@
 
 #define KVM_PTE_LEAF_ATTR_HI_S2_XN	BIT(54)
 
+#define KVM_PTE_LEAF_ATTR_S2_PERMS	(KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R | \
+					 KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W | \
+					 KVM_PTE_LEAF_ATTR_HI_S2_XN)
+
 struct kvm_pgtable_walk_data {
 	struct kvm_pgtable		*pgt;
 	struct kvm_pgtable_walker	*walker;
@@ -460,22 +464,27 @@ static int stage2_map_set_prot_attr(enum kvm_pgtable_prot prot,
 	return 0;
 }
 
-static bool stage2_map_walker_try_leaf(u64 addr, u64 end, u32 level,
-				       kvm_pte_t *ptep,
-				       struct stage2_map_data *data)
+static int stage2_map_walker_try_leaf(u64 addr, u64 end, u32 level,
+				      kvm_pte_t *ptep,
+				      struct stage2_map_data *data)
 {
 	kvm_pte_t new, old = *ptep;
 	u64 granule = kvm_granule_size(level), phys = data->phys;
 	struct page *page = virt_to_page(ptep);
 
 	if (!kvm_block_mapping_supported(addr, end, phys, level))
-		return false;
+		return -E2BIG;
 
 	new = kvm_init_valid_leaf_pte(phys, data->attr, level);
 	if (kvm_pte_valid(old)) {
-		/* Tolerate KVM recreating the exact same mapping */
-		if (old == new)
-			goto out;
+		/*
+		 * Skip updating the PTE if we are trying to recreate the exact
+		 * same mapping or only change the access permissions. Instead,
+		 * the vCPU will exit one more time from guest if still needed
+		 * and then go through the path of relaxing permissions.
+		 */
+		if (!((old ^ new) & (~KVM_PTE_LEAF_ATTR_S2_PERMS)))
+			return -EAGAIN;
 
 		/*
 		 * There's an existing different valid leaf entry, so perform
@@ -488,9 +497,8 @@ static bool stage2_map_walker_try_leaf(u64 addr, u64 end, u32 level,
 
 	smp_store_release(ptep, new);
 	get_page(page);
-out:
 	data->phys += granule;
-	return true;
+	return 0;
 }
 
 static int stage2_map_walk_table_pre(u64 addr, u64 end, u32 level,
@@ -518,6 +526,7 @@ static int stage2_map_walk_table_pre(u64 addr, u64 end, u32 level,
 static int stage2_map_walk_leaf(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
 				struct stage2_map_data *data)
 {
+	int ret;
 	kvm_pte_t *childp, pte = *ptep;
 	struct page *page = virt_to_page(ptep);
 
@@ -528,8 +537,9 @@ static int stage2_map_walk_leaf(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
 		return 0;
 	}
 
-	if (stage2_map_walker_try_leaf(addr, end, level, ptep, data))
-		return 0;
+	ret = stage2_map_walker_try_leaf(addr, end, level, ptep, data);
+	if (ret != -E2BIG)
+		return ret;
 
 	if (WARN_ON(level == KVM_PGTABLE_MAX_LEVELS - 1))
 		return -EINVAL;