diff --git a/headers/private/kernel/vm_page.h b/headers/private/kernel/vm_page.h
index 159d00b5f4..29eed78e48 100644
--- a/headers/private/kernel/vm_page.h
+++ b/headers/private/kernel/vm_page.h
@@ -23,6 +23,8 @@ status_t vm_page_init(struct kernel_args *args);
 status_t vm_page_init_post_area(struct kernel_args *args);
 status_t vm_page_init_post_thread(struct kernel_args *args);
 
+addr_t vm_alloc_virtual_from_kernel_args(kernel_args *ka, size_t size);
+
 status_t vm_mark_page_inuse(addr_t page);
 status_t vm_mark_page_range_inuse(addr_t startPage, addr_t length);
 status_t vm_page_set_state(vm_page *page, int state);
diff --git a/src/system/kernel/arch/generic/generic_vm_physical_page_mapper.cpp b/src/system/kernel/arch/generic/generic_vm_physical_page_mapper.cpp
index ec6e1192dd..b34b8dfdcb 100644
--- a/src/system/kernel/arch/generic/generic_vm_physical_page_mapper.cpp
+++ b/src/system/kernel/arch/generic/generic_vm_physical_page_mapper.cpp
@@ -71,19 +71,20 @@ restart:
 	// map it
 	if (first_free_vmapping < num_virtual_chunks) {
 		// there's a free hole
-		paddr_desc[index].va = first_free_vmapping * sIOSpaceChunkSize + sIOSpaceBase;
+		paddr_desc[index].va = first_free_vmapping * sIOSpaceChunkSize
+			+ sIOSpaceBase;
 		*va = paddr_desc[index].va + pa % sIOSpaceChunkSize;
 		virtual_pmappings[first_free_vmapping] = &paddr_desc[index];
 		paddr_desc[index].ref_count++;
 
 		// push up the first_free_vmapping pointer
-		for (; first_free_vmapping < num_virtual_chunks; first_free_vmapping++) {
+		for (; first_free_vmapping < num_virtual_chunks;
+			 first_free_vmapping++) {
 			if(virtual_pmappings[first_free_vmapping] == NULL)
 				break;
 		}
 
-		sMapIOSpaceChunk(paddr_desc[index].va,
-			index * sIOSpaceChunkSize);
+		sMapIOSpaceChunk(paddr_desc[index].va, index * sIOSpaceChunkSize);
 		mutex_unlock(&iospace_mutex);
 
 		return B_OK;
@@ -150,7 +151,6 @@ generic_put_physical_page(addr_t va)
 
 
 //	#pragma mark -
-//	VM API
 
 
 status_t
@@ -161,10 +161,25 @@ generic_vm_physical_page_mapper_init(kernel_args *args,
 	TRACE(("generic_vm_physical_page_mapper_init: entry\n"));
 
 	sMapIOSpaceChunk = mapIOSpaceChunk;
-	sIOSpaceBase = *ioSpaceBase;
 	sIOSpaceSize = ioSpaceSize;
 	sIOSpaceChunkSize = ioSpaceChunkSize;
 
+	// reserve virtual space for the IO space
+	// We reserve (ioSpaceChunkSize - B_PAGE_SIZE) bytes more, so that we
+	// can guarantee to align the base address to ioSpaceChunkSize.
+	sIOSpaceBase = vm_alloc_virtual_from_kernel_args(args,
+		sIOSpaceSize + ioSpaceChunkSize - B_PAGE_SIZE);
+	if (sIOSpaceBase == 0) {
+		panic("generic_vm_physical_page_mapper_init(): Failed to reserve IO "
+			"space in virtual address space!");
+		return B_ERROR;
+	}
+
+	// align the base address to chunk size
+	sIOSpaceBase = (sIOSpaceBase + ioSpaceChunkSize - 1) / ioSpaceChunkSize
+		* ioSpaceChunkSize;
+	*ioSpaceBase = sIOSpaceBase;
+
 	// allocate some space to hold physical page mapping info
 	paddr_desc = (paddr_chunk_desc *)vm_alloc_from_kernel_args(args,
 		sizeof(paddr_chunk_desc) * 1024, B_KERNEL_READ_AREA | B_KERNEL_WRITE_AREA);
@@ -211,10 +226,6 @@ generic_vm_physical_page_mapper_init_post_area(kernel_args *args)
 	temp = (void *)sIOSpaceBase;
 	area_id ioSpaceArea = vm_create_null_area(vm_kernel_address_space_id(),
 		"iospace", &temp, B_EXACT_ADDRESS, sIOSpaceSize);
-	// TODO: We don't reserve the virtual address space for the IO space in
-	// generic_vm_physical_page_mapper_init() yet. So theoretically it could
-	// happen that a part of that space has been reserved by someone else in
-	// the meantime.
 	if (ioSpaceArea < 0) {
 		panic("generic_vm_physical_page_mapper_init_post_area(): Failed to "
 			"create null area for IO space!\n");
diff --git a/src/system/kernel/arch/x86/arch_vm_translation_map.c b/src/system/kernel/arch/x86/arch_vm_translation_map.c
index 5f87a24411..afef9873a2 100644
--- a/src/system/kernel/arch/x86/arch_vm_translation_map.c
+++ b/src/system/kernel/arch/x86/arch_vm_translation_map.c
@@ -30,8 +30,6 @@
 
 // 256 MB of iospace
 #define IOSPACE_SIZE (256*1024*1024)
-// put it 256 MB into kernel space
-#define IOSPACE_BASE (KERNEL_BASE + IOSPACE_SIZE)
 // 4 MB chunks, to optimize for 4 MB pages
 #define IOSPACE_CHUNK_SIZE (4*1024*1024)
 
@@ -808,7 +806,6 @@ arch_vm_translation_map_init(kernel_args *args)
 	TRACE(("iospace_pgtables %p\n", iospace_pgtables));
 
 	// init physical page mapper
-	sIOSpaceBase = IOSPACE_BASE;
 	error = generic_vm_physical_page_mapper_init(args, map_iospace_chunk,
 		&sIOSpaceBase, IOSPACE_SIZE, IOSPACE_CHUNK_SIZE);
 	if (error != B_OK)
diff --git a/src/system/kernel/vm/vm_page.c b/src/system/kernel/vm/vm_page.c
index bd5654cc44..df9b1a9f5d 100644
--- a/src/system/kernel/vm/vm_page.c
+++ b/src/system/kernel/vm/vm_page.c
@@ -1023,7 +1023,7 @@ static int dump_free_page_table(int argc, char **argv)
 #endif
 
 
-static addr_t
+addr_t
 vm_alloc_virtual_from_kernel_args(kernel_args *ka, size_t size)
 {
 	addr_t spot = 0;
@@ -1048,10 +1048,11 @@ vm_alloc_virtual_from_kernel_args(kernel_args *ka, size_t size)
 	if (spot == 0) {
 		// we hadn't found one between allocation ranges. this is ok.
 		// see if there's a gap after the last one
-		if (ka->virtual_allocated_range[last_valloc_entry].start 
-				+ ka->virtual_allocated_range[last_valloc_entry].size + size 
-			<= KERNEL_BASE + (KERNEL_SIZE - 1)) {
-			spot = ka->virtual_allocated_range[last_valloc_entry].start + ka->virtual_allocated_range[last_valloc_entry].size;
+		addr_t lastRangeEnd
+			= ka->virtual_allocated_range[last_valloc_entry].start 
+				+ ka->virtual_allocated_range[last_valloc_entry].size;
+		if (KERNEL_BASE + (KERNEL_SIZE - 1) - lastRangeEnd >= size) {
+			spot = lastRangeEnd;
 			ka->virtual_allocated_range[last_valloc_entry].size += size;
 			goto out;
 		}