Add dynamic region support to xlat tables lib v2

Added APIs to add and remove regions to the translation tables
dynamically while the MMU is enabled. Only static regions are allowed
to overlap other static ones (for backwards compatibility).

A new private attribute (MT_DYNAMIC / MT_STATIC) has been added to
flag each region as such.

The dynamic mapping functionality can be enabled or disabled when
compiling by setting the build option PLAT_XLAT_TABLES_DYNAMIC to 1
or 0. This can be done per-image.

TLB maintenance code during dynamic table mapping and unmapping has
also been added.

Fixes ARM-software/tf-issues#310

Change-Id: I19e8992005c4292297a382824394490c5387aa3b
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

5 files changed, 598 insertions, 13 deletions

diff --git a/lib/xlat_tables_v2/aarch32/xlat_tables_arch.c b/lib/xlat_tables_v2/aarch32/xlat_tables_arch.c
index 9a08cf8e..7de90304 100644
--- a/lib/xlat_tables_v2/aarch32/xlat_tables_arch.c
+++ b/lib/xlat_tables_v2/aarch32/xlat_tables_arch.c
@@ -50,6 +50,47 @@ int is_mmu_enabled(void)
 	return (read_sctlr() & SCTLR_M_BIT) != 0;
 }
 
+#if PLAT_XLAT_TABLES_DYNAMIC
+
+void xlat_arch_tlbi_va(uintptr_t va)
+{
+	/*
+	 * Ensure the translation table write has drained into memory before
+	 * invalidating the TLB entry.
+	 */
+	dsbishst();
+
+	tlbimvaais(TLBI_ADDR(va));
+}
+
+void xlat_arch_tlbi_va_sync(void)
+{
+	/* Invalidate all entries from branch predictors. */
+	bpiallis();
+
+	/*
+	 * A TLB maintenance instruction can complete at any time after
+	 * it is issued, but is only guaranteed to be complete after the
+	 * execution of DSB by the PE that executed the TLB maintenance
+	 * instruction. After the TLB invalidate instruction is
+	 * complete, no new memory accesses using the invalidated TLB
+	 * entries will be observed by any observer of the system
+	 * domain. See section D4.8.2 of the ARMv8 (issue k), paragraph
+	 * "Ordering and completion of TLB maintenance instructions".
+	 */
+	dsbish();
+
+	/*
+	 * The effects of a completed TLB maintenance instruction are
+	 * only guaranteed to be visible on the PE that executed the
+	 * instruction after the execution of an ISB instruction by the
+	 * PE that executed the TLB maintenance instruction.
+	 */
+	isb();
+}
+
+#endif /* PLAT_XLAT_TABLES_DYNAMIC */
+
 void init_xlat_tables_arch(unsigned long long max_pa)
 {
 	assert((PLAT_PHY_ADDR_SPACE_SIZE - 1) <=
diff --git a/lib/xlat_tables_v2/aarch64/xlat_tables_arch.c b/lib/xlat_tables_v2/aarch64/xlat_tables_arch.c
index 413eaded..25bd2caf 100644
--- a/lib/xlat_tables_v2/aarch64/xlat_tables_arch.c
+++ b/lib/xlat_tables_v2/aarch64/xlat_tables_arch.c
@@ -107,12 +107,66 @@ int is_mmu_enabled(void)
 #endif
 }
 
+#if PLAT_XLAT_TABLES_DYNAMIC
+
+void xlat_arch_tlbi_va(uintptr_t va)
+{
+	/*
+	 * Ensure the translation table write has drained into memory before
+	 * invalidating the TLB entry.
+	 */
+	dsbishst();
+
+#if IMAGE_EL == 1
+	assert(IS_IN_EL(1));
+	tlbivaae1is(TLBI_ADDR(va));
+#elif IMAGE_EL == 3
+	assert(IS_IN_EL(3));
+	tlbivae3is(TLBI_ADDR(va));
+#endif
+}
+
+void xlat_arch_tlbi_va_sync(void)
+{
+	/*
+	 * A TLB maintenance instruction can complete at any time after
+	 * it is issued, but is only guaranteed to be complete after the
+	 * execution of DSB by the PE that executed the TLB maintenance
+	 * instruction. After the TLB invalidate instruction is
+	 * complete, no new memory accesses using the invalidated TLB
+	 * entries will be observed by any observer of the system
+	 * domain. See section D4.8.2 of the ARMv8 (issue k), paragraph
+	 * "Ordering and completion of TLB maintenance instructions".
+	 */
+	dsbish();
+
+	/*
+	 * The effects of a completed TLB maintenance instruction are
+	 * only guaranteed to be visible on the PE that executed the
+	 * instruction after the execution of an ISB instruction by the
+	 * PE that executed the TLB maintenance instruction.
+	 */
+	isb();
+}
+
+#endif /* PLAT_XLAT_TABLES_DYNAMIC */
+
 void init_xlat_tables_arch(unsigned long long max_pa)
 {
 	assert((PLAT_PHY_ADDR_SPACE_SIZE - 1) <=
 	       xlat_arch_get_max_supported_pa());
 
+	/*
+	 * If dynamic allocation of new regions is enabled the code can't make
+	 * assumptions about the max physical address because it could change
+	 * after adding new regions. If this functionality is disabled it is
+	 * safer to restrict the max physical address as much as possible.
+	 */
+#ifdef PLAT_XLAT_TABLES_DYNAMIC
+	tcr_ps_bits = calc_physical_addr_size_bits(PLAT_PHY_ADDR_SPACE_SIZE);
+#else
 	tcr_ps_bits = calc_physical_addr_size_bits(max_pa);
+#endif
 }
 
 /*******************************************************************************
diff --git a/lib/xlat_tables_v2/xlat_tables_common.c b/lib/xlat_tables_v2/xlat_tables_common.c
index 0b17842c..b4691a2b 100644
--- a/lib/xlat_tables_v2/xlat_tables_common.c
+++ b/lib/xlat_tables_v2/xlat_tables_common.c
@@ -60,6 +60,10 @@ static uint64_t tf_base_xlat_table[NUM_BASE_LEVEL_ENTRIES]
 
 static mmap_region_t tf_mmap[MAX_MMAP_REGIONS + 1];
 
+#if PLAT_XLAT_TABLES_DYNAMIC
+static int xlat_tables_mapped_regions[MAX_XLAT_TABLES];
+#endif /* PLAT_XLAT_TABLES_DYNAMIC */
+
 xlat_ctx_t tf_xlat_ctx = {
 
 	.pa_max_address = PLAT_PHY_ADDR_SPACE_SIZE - 1,
@@ -70,6 +74,9 @@ xlat_ctx_t tf_xlat_ctx = {
 
 	.tables = tf_xlat_tables,
 	.tables_num = MAX_XLAT_TABLES,
+#if PLAT_XLAT_TABLES_DYNAMIC
+	.tables_mapped_regions = xlat_tables_mapped_regions,
+#endif /* PLAT_XLAT_TABLES_DYNAMIC */
 
 	.base_table = tf_base_xlat_table,
 	.base_table_entries = NUM_BASE_LEVEL_ENTRIES,
@@ -104,6 +111,27 @@ void mmap_add(const mmap_region_t *mm)
 	}
 }
 
+#if PLAT_XLAT_TABLES_DYNAMIC
+
+int mmap_add_dynamic_region(unsigned long long base_pa,
+			    uintptr_t base_va, size_t size, unsigned int attr)
+{
+	mmap_region_t mm = {
+		.base_va = base_va,
+		.base_pa = base_pa,
+		.size = size,
+		.attr = attr,
+	};
+	return mmap_add_dynamic_region_ctx(&tf_xlat_ctx, &mm);
+}
+
+int mmap_remove_dynamic_region(uintptr_t base_va, size_t size)
+{
+	return mmap_remove_dynamic_region_ctx(&tf_xlat_ctx, base_va, size);
+}
+
+#endif /* PLAT_XLAT_TABLES_DYNAMIC */
+
 void init_xlat_tables(void)
 {
 	assert(!is_mmu_enabled());
diff --git a/lib/xlat_tables_v2/xlat_tables_internal.c b/lib/xlat_tables_v2/xlat_tables_internal.c
index fc4345b9..2f03306e 100644
--- a/lib/xlat_tables_v2/xlat_tables_internal.c
+++ b/lib/xlat_tables_v2/xlat_tables_internal.c
@@ -47,6 +47,63 @@
 #endif
 #include "xlat_tables_private.h"
 
+#if PLAT_XLAT_TABLES_DYNAMIC
+
+/*
+ * The following functions assume that they will be called using subtables only.
+ * The base table can't be unmapped, so it is not needed to do any special
+ * handling for it.
+ */
+
+/*
+ * Returns the index of the array corresponding to the specified translation
+ * table.
+ */
+static int xlat_table_get_index(xlat_ctx_t *ctx, const uint64_t *table)
+{
+	for (int i = 0; i < ctx->tables_num; i++)
+		if (ctx->tables[i] == table)
+			return i;
+
+	/*
+	 * Maybe we were asked to get the index of the base level table, which
+	 * should never happen.
+	 */
+	assert(0);
+
+	return -1;
+}
+
+/* Returns a pointer to an empty translation table. */
+static uint64_t *xlat_table_get_empty(xlat_ctx_t *ctx)
+{
+	for (int i = 0; i < ctx->tables_num; i++)
+		if (ctx->tables_mapped_regions[i] == 0)
+			return ctx->tables[i];
+
+	return NULL;
+}
+
+/* Increments region count for a given table. */
+static void xlat_table_inc_regions_count(xlat_ctx_t *ctx, const uint64_t *table)
+{
+	ctx->tables_mapped_regions[xlat_table_get_index(ctx, table)]++;
+}
+
+/* Decrements region count for a given table. */
+static void xlat_table_dec_regions_count(xlat_ctx_t *ctx, const uint64_t *table)
+{
+	ctx->tables_mapped_regions[xlat_table_get_index(ctx, table)]--;
+}
+
+/* Returns 0 if the speficied table isn't empty, otherwise 1. */
+static int xlat_table_is_empty(xlat_ctx_t *ctx, const uint64_t *table)
+{
+	return !ctx->tables_mapped_regions[xlat_table_get_index(ctx, table)];
+}
+
+#else /* PLAT_XLAT_TABLES_DYNAMIC */
+
 /* Returns a pointer to the first empty translation table. */
 static uint64_t *xlat_table_get_empty(xlat_ctx_t *ctx)
 {
@@ -55,6 +112,8 @@ static uint64_t *xlat_table_get_empty(xlat_ctx_t *ctx)
 	return ctx->tables[ctx->next_table++];
 }
 
+#endif /* PLAT_XLAT_TABLES_DYNAMIC */
+
 /* Returns a block/page table descriptor for the given level and attributes. */
 static uint64_t xlat_desc(unsigned int attr, unsigned long long addr_pa,
 			  int level)
@@ -156,6 +215,142 @@ typedef enum {
 
 } action_t;
 
+#if PLAT_XLAT_TABLES_DYNAMIC
+
+/*
+ * Recursive function that writes to the translation tables and unmaps the
+ * specified region.
+ */
+static void xlat_tables_unmap_region(xlat_ctx_t *ctx, mmap_region_t *mm,
+				     const uintptr_t table_base_va,
+				     uint64_t *const table_base,
+				     const int table_entries,
+				     const int level)
+{
+	assert(level >= ctx->base_level && level <= XLAT_TABLE_LEVEL_MAX);
+
+	uint64_t *subtable;
+	uint64_t desc;
+
+	uintptr_t table_idx_va;
+	uintptr_t table_idx_end_va; /* End VA of this entry */
+
+	uintptr_t region_end_va = mm->base_va + mm->size - 1;
+
+	int table_idx;
+
+	if (mm->base_va > table_base_va) {
+		/* Find the first index of the table affected by the region. */
+		table_idx_va = mm->base_va & ~XLAT_BLOCK_MASK(level);
+
+		table_idx = (table_idx_va - table_base_va) >>
+			    XLAT_ADDR_SHIFT(level);
+
+		assert(table_idx < table_entries);
+	} else {
+		/* Start from the beginning of the table. */
+		table_idx_va = table_base_va;
+		table_idx = 0;
+	}
+
+	while (table_idx < table_entries) {
+
+		table_idx_end_va = table_idx_va + XLAT_BLOCK_SIZE(level) - 1;
+
+		desc = table_base[table_idx];
+		uint64_t desc_type = desc & DESC_MASK;
+
+		action_t action = ACTION_NONE;
+
+		if ((mm->base_va <= table_idx_va) &&
+		    (region_end_va >= table_idx_end_va)) {
+
+			/* Region covers all block */
+
+			if (level == 3) {
+				/*
+				 * Last level, only page descriptors allowed,
+				 * erase it.
+				 */
+				assert(desc_type == PAGE_DESC);
+
+				action = ACTION_WRITE_BLOCK_ENTRY;
+			} else {
+				/*
+				 * Other levels can have table descriptors. If
+				 * so, recurse into it and erase descriptors
+				 * inside it as needed. If there is a block
+				 * descriptor, just erase it. If an invalid
+				 * descriptor is found, this table isn't
+				 * actually mapped, which shouldn't happen.
+				 */
+				if (desc_type == TABLE_DESC) {
+					action = ACTION_RECURSE_INTO_TABLE;
+				} else {
+					assert(desc_type == BLOCK_DESC);
+					action = ACTION_WRITE_BLOCK_ENTRY;
+				}
+			}
+
+		} else if ((mm->base_va <= table_idx_end_va) ||
+			   (region_end_va >= table_idx_va)) {
+
+			/*
+			 * Region partially covers block.
+			 *
+			 * It can't happen in level 3.
+			 *
+			 * There must be a table descriptor here, if not there
+			 * was a problem when mapping the region.
+			 */
+
+			assert(level < 3);
+
+			assert(desc_type == TABLE_DESC);
+
+			action = ACTION_RECURSE_INTO_TABLE;
+		}
+
+		if (action == ACTION_WRITE_BLOCK_ENTRY) {
+
+			table_base[table_idx] = INVALID_DESC;
+			xlat_arch_tlbi_va(table_idx_va);
+
+		} else if (action == ACTION_RECURSE_INTO_TABLE) {
+
+			subtable = (uint64_t *)(uintptr_t)(desc & TABLE_ADDR_MASK);
+
+			/* Recurse to write into subtable */
+			xlat_tables_unmap_region(ctx, mm, table_idx_va,
+						 subtable, XLAT_TABLE_ENTRIES,
+						 level + 1);
+
+			/*
+			 * If the subtable is now empty, remove its reference.
+			 */
+			if (xlat_table_is_empty(ctx, subtable)) {
+				table_base[table_idx] = INVALID_DESC;
+				xlat_arch_tlbi_va(table_idx_va);
+			}
+
+		} else {
+			assert(action == ACTION_NONE);
+		}
+
+		table_idx++;
+		table_idx_va += XLAT_BLOCK_SIZE(level);
+
+		/* If reached the end of the region, exit */
+		if (region_end_va <= table_idx_va)
+			break;
+	}
+
+	if (level > ctx->base_level)
+		xlat_table_dec_regions_count(ctx, table_base);
+}
+
+#endif /* PLAT_XLAT_TABLES_DYNAMIC */
+
 /*
  * From the given arguments, it decides which action to take when mapping the
  * specified region.
@@ -287,9 +482,11 @@ static action_t xlat_tables_map_region_action(const mmap_region_t *mm,
 
 /*
  * Recursive function that writes to the translation tables and maps the
- * specified region.
+ * specified region. On success, it returns the VA of the last byte that was
+ * succesfully mapped. On error, it returns the VA of the next entry that
+ * should have been mapped.
  */
-static void xlat_tables_map_region(xlat_ctx_t *ctx, mmap_region_t *mm,
+static uintptr_t xlat_tables_map_region(xlat_ctx_t *ctx, mmap_region_t *mm,
 				   const uintptr_t table_base_va,
 				   uint64_t *const table_base,
 				   const int table_entries,
@@ -321,6 +518,11 @@ static void xlat_tables_map_region(xlat_ctx_t *ctx, mmap_region_t *mm,
 		table_idx = 0;
 	}
 
+#if PLAT_XLAT_TABLES_DYNAMIC
+	if (level > ctx->base_level)
+		xlat_table_inc_regions_count(ctx, table_base);
+#endif
+
 	while (table_idx < table_entries) {
 
 		desc = table_base[table_idx];
@@ -338,20 +540,30 @@ static void xlat_tables_map_region(xlat_ctx_t *ctx, mmap_region_t *mm,
 		} else if (action == ACTION_CREATE_NEW_TABLE) {
 
 			subtable = xlat_table_get_empty(ctx);
-			assert(subtable != NULL);
-			/* Recurse to write into subtable */
-			xlat_tables_map_region(ctx, mm, table_idx_va, subtable,
-					       XLAT_TABLE_ENTRIES, level + 1);
+			if (subtable == NULL) {
+				/* Not enough free tables to map this region */
+				return table_idx_va;
+			}
+
 			/* Point to new subtable from this one. */
-			table_base[table_idx] =
-					TABLE_DESC | (unsigned long)subtable;
+			table_base[table_idx] = TABLE_DESC | (unsigned long)subtable;
+
+			/* Recurse to write into subtable */
+			uintptr_t end_va = xlat_tables_map_region(ctx, mm, table_idx_va,
+					       subtable, XLAT_TABLE_ENTRIES,
+					       level + 1);
+			if (end_va != table_idx_va + XLAT_BLOCK_SIZE(level) - 1)
+				return end_va;
 
 		} else if (action == ACTION_RECURSE_INTO_TABLE) {
 
 			subtable = (uint64_t *)(uintptr_t)(desc & TABLE_ADDR_MASK);
 			/* Recurse to write into subtable */
-			xlat_tables_map_region(ctx, mm, table_idx_va, subtable,
-					       XLAT_TABLE_ENTRIES, level + 1);
+			uintptr_t end_va =  xlat_tables_map_region(ctx, mm, table_idx_va,
+					       subtable, XLAT_TABLE_ENTRIES,
+					       level + 1);
+			if (end_va != table_idx_va + XLAT_BLOCK_SIZE(level) - 1)
+				return end_va;
 
 		} else {
 
@@ -366,6 +578,8 @@ static void xlat_tables_map_region(xlat_ctx_t *ctx, mmap_region_t *mm,
 		if (mm_end_va <= table_idx_va)
 			break;
 	}
+
+	return table_idx_va - 1;
 }
 
 void print_mmap(mmap_region_t *const mmap)
@@ -436,10 +650,14 @@ static int mmap_add_region_check(xlat_ctx_t *ctx, unsigned long long base_pa,
 		 * Full VA overlaps are only allowed if both regions are
 		 * identity mapped (zero offset) or have the same VA to PA
 		 * offset. Also, make sure that it's not the exact same area.
-		 * This can only be done with locked regions.
+		 * This can only be done with static regions.
 		 */
 		if (fully_overlapped_va) {
 
+#if PLAT_XLAT_TABLES_DYNAMIC
+			if ((attr & MT_DYNAMIC) || (mm->attr & MT_DYNAMIC))
+				return -EPERM;
+#endif /* PLAT_XLAT_TABLES_DYNAMIC */
 			if ((mm->base_va - mm->base_pa) != (base_va - base_pa))
 				return -EPERM;
 
@@ -481,6 +699,9 @@ void mmap_add_region_ctx(xlat_ctx_t *ctx, mmap_region_t *mm)
 	if (!mm->size)
 		return;
 
+	/* Static regions must be added before initializing the xlat tables. */
+	assert(!ctx->initialized);
+
 	ret = mmap_add_region_check(ctx, mm->base_pa, mm->base_va, mm->size,
 				    mm->attr);
 	if (ret != 0) {
@@ -509,6 +730,8 @@ void mmap_add_region_ctx(xlat_ctx_t *ctx, mmap_region_t *mm)
 	 * regions with the loop in xlat_tables_init_internal because the outer
 	 * ones won't overwrite block or page descriptors of regions added
 	 * previously.
+	 *
+	 * Overlapping is only allowed for static regions.
 	 */
 
 	while ((mm_cursor->base_va + mm_cursor->size - 1) < end_va
@@ -541,6 +764,179 @@ void mmap_add_region_ctx(xlat_ctx_t *ctx, mmap_region_t *mm)
 		ctx->max_va = end_va;
 }
 
+#if PLAT_XLAT_TABLES_DYNAMIC
+
+int mmap_add_dynamic_region_ctx(xlat_ctx_t *ctx, mmap_region_t *mm)
+{
+	mmap_region_t *mm_cursor = ctx->mmap;
+	mmap_region_t *mm_last = mm_cursor + ctx->mmap_num;
+	unsigned long long end_pa = mm->base_pa + mm->size - 1;
+	uintptr_t end_va = mm->base_va + mm->size - 1;
+	int ret;
+
+	/* Nothing to do */
+	if (!mm->size)
+		return 0;
+
+	ret = mmap_add_region_check(ctx, mm->base_pa, mm->base_va, mm->size, mm->attr | MT_DYNAMIC);
+	if (ret != 0)
+		return ret;
+
+	/*
+	 * Find the adequate entry in the mmap array in the same way done for
+	 * static regions in mmap_add_region_ctx().
+	 */
+
+	while ((mm_cursor->base_va + mm_cursor->size - 1) < end_va && mm_cursor->size)
+		++mm_cursor;
+
+	while ((mm_cursor->base_va + mm_cursor->size - 1 == end_va) && (mm_cursor->size < mm->size))
+		++mm_cursor;
+
+	/* Make room for new region by moving other regions up by one place */
+	memmove(mm_cursor + 1, mm_cursor, (uintptr_t)mm_last - (uintptr_t)mm_cursor);
+
+	/*
+	 * Check we haven't lost the empty sentinal from the end of the array.
+	 * This shouldn't happen as we have checked in mmap_add_region_check
+	 * that there is free space.
+	 */
+	assert(mm_last->size == 0);
+
+	mm_cursor->base_pa = mm->base_pa;
+	mm_cursor->base_va = mm->base_va;
+	mm_cursor->size = mm->size;
+	mm_cursor->attr = mm->attr | MT_DYNAMIC;
+
+	/*
+	 * Update the translation tables if the xlat tables are initialized. If
+	 * not, this region will be mapped when they are initialized.
+	 */
+	if (ctx->initialized) {
+		uintptr_t end_va = xlat_tables_map_region(ctx, mm_cursor, 0, ctx->base_table,
+				ctx->base_table_entries, ctx->base_level);
+
+		/* Failed to map, remove mmap entry, unmap and return error. */
+		if (end_va != mm_cursor->base_va + mm_cursor->size - 1) {
+			memmove(mm_cursor, mm_cursor + 1, (uintptr_t)mm_last - (uintptr_t)mm_cursor);
+
+			/*
+			 * Check if the mapping function actually managed to map
+			 * anything. If not, just return now.
+			 */
+			if (mm_cursor->base_va >= end_va)
+				return -ENOMEM;
+
+			/*
+			 * Something went wrong after mapping some table entries,
+			 * undo every change done up to this point.
+			 */
+			mmap_region_t unmap_mm = {
+					.base_pa = 0,
+					.base_va = mm->base_va,
+					.size = end_va - mm->base_va,
+					.attr = 0
+			};
+			xlat_tables_unmap_region(ctx, &unmap_mm, 0, ctx->base_table,
+							ctx->base_table_entries, ctx->base_level);
+
+			return -ENOMEM;
+		}
+
+		/*
+		 * Make sure that all entries are written to the memory. There
+		 * is no need to invalidate entries when mapping dynamic regions
+		 * because new table/block/page descriptors only replace old
+		 * invalid descriptors, that aren't TLB cached.
+		 */
+		dsbishst();
+	}
+
+	if (end_pa > ctx->max_pa)
+		ctx->max_pa = end_pa;
+	if (end_va > ctx->max_va)
+		ctx->max_va = end_va;
+
+	return 0;
+}
+
+/*
+ * Removes the region with given base Virtual Address and size from the given
+ * context.
+ *
+ * Returns:
+ *        0: Success.
+ *   EINVAL: Invalid values were used as arguments (region not found).
+ *    EPERM: Tried to remove a static region.
+ */
+int mmap_remove_dynamic_region_ctx(xlat_ctx_t *ctx, uintptr_t base_va,
+				   size_t size)
+{
+	mmap_region_t *mm = ctx->mmap;
+	mmap_region_t *mm_last = mm + ctx->mmap_num;
+	int update_max_va_needed = 0;
+	int update_max_pa_needed = 0;
+
+	/* Check sanity of mmap array. */
+	assert(mm[ctx->mmap_num].size == 0);
+
+	while (mm->size) {
+		if ((mm->base_va == base_va) && (mm->size == size))
+			break;
+		++mm;
+	}
+
+	/* Check that the region was found */
+	if (mm->size == 0)
+		return -EINVAL;
+
+	/* If the region is static it can't be removed */
+	if (!(mm->attr & MT_DYNAMIC))
+		return -EPERM;
+
+	/* Check if this region is using the top VAs or PAs. */
+	if ((mm->base_va + mm->size - 1) == ctx->max_va)
+		update_max_va_needed = 1;
+	if ((mm->base_pa + mm->size - 1) == ctx->max_pa)
+		update_max_pa_needed = 1;
+
+	/* Update the translation tables if needed */
+	if (ctx->initialized) {
+		xlat_tables_unmap_region(ctx, mm, 0, ctx->base_table,
+					 ctx->base_table_entries,
+					 ctx->base_level);
+		xlat_arch_tlbi_va_sync();
+	}
+
+	/* Remove this region by moving the rest down by one place. */
+	memmove(mm, mm + 1, (uintptr_t)mm_last - (uintptr_t)mm);
+
+	/* Check if we need to update the max VAs and PAs */
+	if (update_max_va_needed) {
+		ctx->max_va = 0;
+		mm = ctx->mmap;
+		while (mm->size) {
+			if ((mm->base_va + mm->size - 1) > ctx->max_va)
+				ctx->max_va = mm->base_va + mm->size - 1;
+			++mm;
+		}
+	}
+
+	if (update_max_pa_needed) {
+		ctx->max_pa = 0;
+		mm = ctx->mmap;
+		while (mm->size) {
+			if ((mm->base_pa + mm->size - 1) > ctx->max_pa)
+				ctx->max_pa = mm->base_pa + mm->size - 1;
+			++mm;
+		}
+	}
+
+	return 0;
+}
+
+#endif /* PLAT_XLAT_TABLES_DYNAMIC */
+
 #if LOG_LEVEL >= LOG_LEVEL_VERBOSE
 
 /* Print the attributes of the specified block descriptor. */
@@ -681,13 +1077,26 @@ void init_xlation_table(xlat_ctx_t *ctx)
 		ctx->base_table[i] = INVALID_DESC;
 
 	for (int j = 0; j < ctx->tables_num; j++) {
+#if PLAT_XLAT_TABLES_DYNAMIC
+		ctx->tables_mapped_regions[j] = 0;
+#endif
 		for (int i = 0; i < XLAT_TABLE_ENTRIES; i++)
 			ctx->tables[j][i] = INVALID_DESC;
 	}
 
-	while (mm->size)
-		xlat_tables_map_region(ctx, mm++, 0, ctx->base_table,
+	while (mm->size) {
+		uintptr_t end_va = xlat_tables_map_region(ctx, mm, 0, ctx->base_table,
 				ctx->base_table_entries, ctx->base_level);
 
+		if (end_va != mm->base_va + mm->size - 1) {
+			ERROR("Not enough memory to map region:\n"
+			      " VA:%p  PA:0x%llx  size:0x%zx  attr:0x%x\n",
+			      (void *)mm->base_va, mm->base_pa, mm->size, mm->attr);
+			panic();
+		}
+
+		mm++;
+	}
+
 	ctx->initialized = 1;
 }
diff --git a/lib/xlat_tables_v2/xlat_tables_private.h b/lib/xlat_tables_v2/xlat_tables_private.h
index 4b484052..048c4a83 100644
--- a/lib/xlat_tables_v2/xlat_tables_private.h
+++ b/lib/xlat_tables_v2/xlat_tables_private.h
@@ -82,6 +82,13 @@ typedef struct {
 	 */
 	uint64_t (*tables)[XLAT_TABLE_ENTRIES];
 	int tables_num;
+	/*
+	 * Keep track of how many regions are mapped in each table. The base
+	 * table can't be unmapped so it isn't needed to keep track of it.
+	 */
+#if PLAT_XLAT_TABLES_DYNAMIC
+	int *tables_mapped_regions;
+#endif /* PLAT_XLAT_TABLES_DYNAMIC */
 
 	int next_table;
 
@@ -103,6 +110,52 @@ typedef struct {
 
 } xlat_ctx_t;
 
+#if PLAT_XLAT_TABLES_DYNAMIC
+/*
+ * Shifts and masks to access fields of an mmap_attr_t
+ */
+/* Dynamic or static */
+#define MT_DYN_SHIFT		30 /* 31 would cause undefined behaviours */
+
+/*
+ * Memory mapping private attributes
+ *
+ * Private attributes not exposed in the mmap_attr_t enum.
+ */
+typedef enum  {
+	/*
+	 * Regions mapped before the MMU can't be unmapped dynamically (they are
+	 * static) and regions mapped with MMU enabled can be unmapped. This
+	 * behaviour can't be overridden.
+	 *
+	 * Static regions can overlap each other, dynamic regions can't.
+	 */
+	MT_STATIC	= 0 << MT_DYN_SHIFT,
+	MT_DYNAMIC	= 1 << MT_DYN_SHIFT
+} mmap_priv_attr_t;
+
+/*
+ * Function used to invalidate all levels of the translation walk for a given
+ * virtual address. It must be called for every translation table entry that is
+ * modified.
+ */
+void xlat_arch_tlbi_va(uintptr_t va);
+
+/*
+ * This function has to be called at the end of any code that uses the function
+ * xlat_arch_tlbi_va().
+ */
+void xlat_arch_tlbi_va_sync(void);
+
+/* Add a dynamic region to the specified context. */
+int mmap_add_dynamic_region_ctx(xlat_ctx_t *ctx, mmap_region_t *mm);
+
+/* Remove a dynamic region from the specified context. */
+int mmap_remove_dynamic_region_ctx(xlat_ctx_t *ctx, uintptr_t base_va,
+			size_t size);
+
+#endif /* PLAT_XLAT_TABLES_DYNAMIC */
+
 /* Print VA, PA, size and attributes of all regions in the mmap array. */
 void print_mmap(mmap_region_t *const mmap);