Reload cr3 after updating P4

src/kernel/boot/boot.S

@@ -43,7 +43,7 @@ _start:
   lgdt [V2P(BootGDTp)]
 
   //; and update the code selector by a long jump
-  jmp 0x8:V2P(long_mode_start)
+jmp 0x8:V2P(long_mode_start)
 
 .code64
   long_mode_start:
@@ -68,6 +68,9 @@ _start:
   mov rax, 0
   movabs [BootP4], rax
 
+  mov rax, cr3
+  mov cr3, rax
+
   //; Jump to kmain()
 .extern kmain
   movabs rax, offset kmain