1 files changed, 85 insertions, 4 deletions

diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index f4a514a2e7ae..dc6ef2cfe3eb 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -48,6 +48,8 @@
 					 KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W | \
 					 KVM_PTE_LEAF_ATTR_HI_S2_XN)
 
+#define KVM_PTE_LEAF_ATTR_S2_IGNORED	GENMASK(58, 55)
+
 #define KVM_INVALID_PTE_OWNER_MASK	GENMASK(63, 56)
 #define KVM_MAX_OWNER_ID		1
 
@@ -77,15 +79,20 @@ static bool kvm_phys_is_valid(u64 phys)
 	return phys < BIT(id_aa64mmfr0_parange_to_phys_shift(ID_AA64MMFR0_PARANGE_MAX));
 }
 
-static bool kvm_block_mapping_supported(u64 addr, u64 end, u64 phys, u32 level)
+static bool kvm_level_supports_block_mapping(u32 level)
 {
-	u64 granule = kvm_granule_size(level);
-
 	/*
 	 * Reject invalid block mappings and don't bother with 4TB mappings for
 	 * 52-bit PAs.
 	 */
-	if (level == 0 || (PAGE_SIZE != SZ_4K && level == 1))
+	return !(level == 0 || (PAGE_SIZE != SZ_4K && level == 1));
+}
+
+static bool kvm_block_mapping_supported(u64 addr, u64 end, u64 phys, u32 level)
+{
+	u64 granule = kvm_granule_size(level);
+
+	if (!kvm_level_supports_block_mapping(level))
 		return false;
 
 	if (granule > (end - addr))
@@ -1053,3 +1060,77 @@ void kvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt)
 	pgt->mm_ops->free_pages_exact(pgt->pgd, pgd_sz);
 	pgt->pgd = NULL;
 }
+
+#define KVM_PTE_LEAF_S2_COMPAT_MASK	(KVM_PTE_LEAF_ATTR_S2_PERMS | \
+					 KVM_PTE_LEAF_ATTR_LO_S2_MEMATTR | \
+					 KVM_PTE_LEAF_ATTR_S2_IGNORED)
+
+static int stage2_check_permission_walker(u64 addr, u64 end, u32 level,
+					  kvm_pte_t *ptep,
+					  enum kvm_pgtable_walk_flags flag,
+					  void * const arg)
+{
+	kvm_pte_t old_attr, pte = *ptep, *new_attr = arg;
+
+	/*
+	 * Compatible mappings are either invalid and owned by the page-table
+	 * owner (whose id is 0), or valid with matching permission attributes.
+	 */
+	if (kvm_pte_valid(pte)) {
+		old_attr = pte & KVM_PTE_LEAF_S2_COMPAT_MASK;
+		if (old_attr != *new_attr)
+			return -EEXIST;
+	} else if (pte) {
+		return -EEXIST;
+	}
+
+	return 0;
+}
+
+int kvm_pgtable_stage2_find_range(struct kvm_pgtable *pgt, u64 addr,
+				  enum kvm_pgtable_prot prot,
+				  struct kvm_mem_range *range)
+{
+	kvm_pte_t attr;
+	struct kvm_pgtable_walker check_perm_walker = {
+		.cb		= stage2_check_permission_walker,
+		.flags		= KVM_PGTABLE_WALK_LEAF,
+		.arg		= &attr,
+	};
+	u64 granule, start, end;
+	u32 level;
+	int ret;
+
+	ret = stage2_set_prot_attr(prot, &attr);
+	if (ret)
+		return ret;
+	attr &= KVM_PTE_LEAF_S2_COMPAT_MASK;
+
+	for (level = pgt->start_level; level < KVM_PGTABLE_MAX_LEVELS; level++) {
+		granule = kvm_granule_size(level);
+		start = ALIGN_DOWN(addr, granule);
+		end = start + granule;
+
+		if (!kvm_level_supports_block_mapping(level))
+			continue;
+
+		if (start < range->start || range->end < end)
+			continue;
+
+		/*
+		 * Check the presence of existing mappings with incompatible
+		 * permissions within the current block range, and try one level
+		 * deeper if one is found.
+		 */
+		ret = kvm_pgtable_walk(pgt, start, granule, &check_perm_walker);
+		if (ret != -EEXIST)
+			break;
+	}
+
+	if (!ret) {
+		range->start = start;
+		range->end = end;
+	}
+
+	return ret;
+}