diff --git a/Makefile b/Makefile
index b50a39b..4d981d4 100644
--- a/Makefile
+++ b/Makefile
@@ -16,12 +16,14 @@ QEMU_ARGS := -monitor stdio \
 			 -bios /usr/share/ovmf/OVMF.fd \
 			 -m 8192 \
 			 -M q35 \
+			 -usb \
+			 -device usb-host \
 			 -vga virtio \
 			 -no-reboot \
 			 -D qemu.log \
 			-drive format=raw,file=
 
-QEMU_DEBUG_ARGS:= -no-shutdown -d int -s -S $(QEMU_ARGS)
+QEMU_DEBUG_ARGS:= -no-shutdown -d int $(QEMU_ARGS)
 
 
 run: all
diff --git a/core b/core
deleted file mode 100644
index c6652c8..0000000
Binary files a/core and /dev/null differ
diff --git a/kernel/drivers/pcie.c b/kernel/drivers/pcie.c
index 63edfa5..ae92aae 100644
--- a/kernel/drivers/pcie.c
+++ b/kernel/drivers/pcie.c
@@ -111,11 +111,13 @@ static void scan_devices(void) {
                 unsigned func, 
                 struct PCIE_configuration_space* config_space
                 ) {
+                    
         current->next = kmalloc(
                     sizeof(struct device_desc_node)
                 );
 
-        
+        klog_debug("device %u:%u - %u", bus, device, func);
+
         current = current->next;
         current->next           = NULL;
 
@@ -136,15 +138,17 @@ static void scan_devices(void) {
             // the device
             if(!check_function(bus,device, 0))
                 continue;
+
             insert(bus, device, 0, get_config_space_base(bus,device,0));
             
-            for(unsigned func = 0; func < 8; func++)
+            for(unsigned func = 1; func < 8; func++)
                 if(check_function(bus,device, func))
                     insert(bus, device, func, get_config_space_base(bus,device,func));
 
         }
     }
     
+
     // now create the final array
     installed_devices = kmalloc(
                     n_installed_devices 
@@ -165,7 +169,27 @@ static void scan_devices(void) {
         kfree(device);
         device = next;
     }
+}
+// identity map every page that might be a config space 
+static void identity_map_possible_config_spaces(void) {
+    for(unsigned i = 0; i < pcie_descriptor.size; i++) {
 
+        // identity map the corresponding pages
+        map_pages(
+            (uint64_t)pcie_descriptor.array[i].address, // phys
+            (uint64_t)pcie_descriptor.array[i].address, // virt
+            256 * // busses
+            32  * // devices
+            8,    // functions
+            PRESENT_ENTRY | PCD | PL_XD
+            // no cache, execute disable
+        );
+    }
+}
+
+static void identity_unmap_possible_config_spaces(void) {
+    for(unsigned i = 0; i < pcie_descriptor.size; i++)
+    ;//    unmap_pages((uint64_t)pcie_descriptor.array[i].address, 256 * 32 * 8);
 }
 
 /**
@@ -178,28 +202,20 @@ void pcie_init(void) {
     klog_debug("init pcie...");
 
     // calculate the highest bus number
+
     for(unsigned i = 0; i < pcie_descriptor.size; i++) {
         // map the corresponding pages 
         if(pcie_descriptor.array[i].end_bus > max_bus)
             max_bus = pcie_descriptor.array[i].end_bus;
+    }
 
-        klog_debug("map %lx", pcie_descriptor.array[i].address);
-        // identity map the corresponding pages
-        map_pages(
-            pcie_descriptor.array[i].address, // phys
-            pcie_descriptor.array[i].address, // virt
-            256 * // busses
-            32  * // devices
-            8   ,     // functions
-            PRESENT_ENTRY | PCD | PL_XD
-            // no cache, execute disable
-        );
+    identity_map_possible_config_spaces();
+    
+    scan_devices();
 
 
-    }
-    asm("hlt");
+    identity_unmap_possible_config_spaces();
 
-    scan_devices();
 
     klog_info("found %u PCI Express devices", n_installed_devices);
 }
\ No newline at end of file
diff --git a/kernel/memory/kalloc.c b/kernel/memory/kalloc.c
index 8449632..d230bf6 100644
--- a/kernel/memory/kalloc.c
+++ b/kernel/memory/kalloc.c
@@ -80,12 +80,13 @@ static void expand_heap(size_t size) {
     size_t new_kheap_pages_size = (kheap_size + size + 0xfff) >> 12;
     size_t old_kheap_pages_size = (kheap_size        + 0xfff) >> 12;
 
+
 // alloc extra pages if needed
     if(new_kheap_pages_size != old_kheap_pages_size) {
         alloc_pages(
             kheap_begin + (old_kheap_pages_size << 12),
             new_kheap_pages_size - old_kheap_pages_size,
-            PRESENT_ENTRY// | PL_XD // execute disable pages
+            PRESENT_ENTRY | PL_XD // execute disable pages
         );
     }
 
@@ -245,7 +246,9 @@ static seg_header* split_segment(seg_header* pred, seg_header* tosplit, size_t s
 
 
 void kheap_init(void) {
+
     klog_debug("init kernel heap...");
+
     expand_heap(MIN_EXPAND_SIZE);
 }
 
diff --git a/kernel/memory/paging.c b/kernel/memory/paging.c
index 2111068..dde5ed5 100644
--- a/kernel/memory/paging.c
+++ b/kernel/memory/paging.c
@@ -17,11 +17,12 @@
 #define IA32_EFER_NXE_BIT (1lu << 11)
 
 // size of bulks of allocation
-// the page buffer is 64 long
-// so we suppose that 4096 pages
-// won't make more than 64 page
-// tables
-#define MAX_ALLOC 1024
+// the page buffer is 16 long
+// in the worst case scenario,
+// 8192 page allocs 
+// -> 1 pdpt + 1 pd + 9 pt 
+// = 11 newpages
+#define MAX_ALLOC 4096
 
 
 /**
@@ -244,7 +245,6 @@ static void map_kernel(const struct stivale2_struct_tag_memmap* memmap) {
                 break;
             default:
                 /* data */
-                flags |=  PL_XD;
                 break;
             }
             //alloc the page table pages
@@ -426,6 +426,7 @@ static void* get_entry_or_allocate(void** restrict table, unsigned index)  {
     void* entry = virtual_addr_table[index];
 
     if(!present_entry(entry)) {
+
         void* e = create_table_entry(
             alloc_page_table(), 
             PRESENT_ENTRY);
@@ -435,6 +436,19 @@ static void* get_entry_or_allocate(void** restrict table, unsigned index)  {
         return entry;
 }
 
+// kernel panic if the entrty is not present
+static void* get_entry_or_panic(void** restrict table, unsigned index)  {
+    assert(index < 512);
+
+    void** virtual_addr_table =  translate_address(table);
+
+    void* entry = virtual_addr_table[index];
+
+    assert(present_entry(entry));
+    
+    return entry;
+}
+
 /**
  * this function cannot be called in a callback
  * because it would lead to recursion.
@@ -447,6 +461,7 @@ static void internal_map_pages(uint64_t physical_addr,
                                uint64_t flags) {
     
     while(count > 0) {
+        
         // fetch table indexes
         unsigned pml4i = pml4_offset(virtual_addr),
                 pdpti = pdpt_offset(virtual_addr),
@@ -499,19 +514,16 @@ void alloc_pages(void*  virtual_addr_begin,
     // don't allow recusion
     alloc_page_table_realloc = 0;
 
-
     void callback(
             uint64_t physical_address, 
             uint64_t virtual_address,
             size_t   c) {
-            
         
         internal_map_pages(physical_address,
                   virtual_address,
                   c,
                   flags);
     };
-
     while(count > 0) {
         unsigned size = count;
         if(size > MAX_ALLOC)
@@ -544,4 +556,73 @@ void map_pages(uint64_t physical_addr,
     // count <= 64
     fill_page_table_allocator_buffer(64);
     internal_map_pages(physical_addr, virtual_addr, count, flags);
-}
\ No newline at end of file
+}
+
+// return 1 if any of the page entries is present
+int is_range_unmapped(pte* page_table, unsigned begin, unsigned end) {
+
+    pte* translated = translate_address(page_table);
+
+    for(int i = begin; i < end; i++) {
+        if(present_entry(translated[i]))
+            return 1;
+    }
+    return 0;
+}
+
+void unmap_pages(uint64_t virtual_addr, size_t count) {
+
+    while(count > 0) {
+        // fetch table indexes
+        unsigned pml4i = pml4_offset(virtual_addr),
+                 pdpti = pdpt_offset(virtual_addr),
+                 pdi   = pd_offset(virtual_addr),
+                 pti   = pt_offset(virtual_addr);
+
+        assert(pml4i == 0 || pml4i == 511 || pml4i == 256);
+        // those entries should exist
+
+        pml4e restrict pml4entry = extract_pointer(get_entry_or_panic((void**)pml4,      pml4i));
+        pdpte restrict pdptentry = extract_pointer(get_entry_or_panic((void**)pml4entry, pdpti));
+        pde   restrict pdentry   = extract_pointer(get_entry_or_panic((void**)pdptentry, pdi));
+
+        // keep track of the first & last element
+        // to unmap, we are sure that in this range
+        // everything is unmapped
+        unsigned begin = pti;
+
+        while(count > 0 && pti < 512) {
+            void** entry_ptr = (void**)translate_address(pdentry) + pti;
+            
+
+            if(!present_entry(*entry_ptr)) {
+
+                char buff[256];
+
+                sprintf(buff, 
+                    "unmap_pages(...):\n"
+                    " tried to unmap not mapped virtual memory 0x%lx",
+                    virtual_addr);
+                
+                panic(buff);
+            }
+
+            pti++;
+            count--;
+            virtual_addr  += 0x1000;      
+        }
+        
+        unsigned end = pti;
+
+        // unmap the page map if empty
+        if(is_range_unmapped(pdentry, 0, begin))
+            continue;
+        if(is_range_unmapped(pdentry, end, 512))
+            continue;
+        
+        // the page table contains no entry
+        // let's free it
+        physfree(pdentry);
+
+    }
+}
diff --git a/kernel/memory/paging.h b/kernel/memory/paging.h
index 0b4af2e..d7c9dd0 100644
--- a/kernel/memory/paging.h
+++ b/kernel/memory/paging.h
@@ -46,6 +46,8 @@ void map_pages(uint64_t physical_addr,
                size_t   count,
                uint64_t flags);
 
+void unmap_pages(uint64_t virtual_addr, size_t count);
+
 void alloc_pages(void* virtual_addr, 
                size_t   count,
                uint64_t flags);
diff --git a/kernel/memory/vmap.h b/kernel/memory/vmap.h
index 342ee15..e990723 100644
--- a/kernel/memory/vmap.h
+++ b/kernel/memory/vmap.h
@@ -111,6 +111,6 @@ static inline uint64_t early_virtual_to_physical(
 
 // translate a physical memory address
 // to access it where it is mapped
-static inline void* translate_address(void* phys_addr) {
+static inline void* __attribute__((pure)) translate_address(void* phys_addr) {
     return (void*)((uint64_t)phys_addr | TRANSLATED_PHYSICAL_MEMORY_BEGIN);
 }
diff --git a/kernel/video/terminal.h b/kernel/video/terminal.h
index f46d3d1..16595d9 100644
--- a/kernel/video/terminal.h
+++ b/kernel/video/terminal.h
@@ -38,6 +38,7 @@ void terminal_clear(void);
 
 // change the default terminal handler,
 // which is an empty function
+// h = NULL will make a safe empty handler
 void set_terminal_handler(terminal_handler_t h);