Index: kernel/arch/amd64/src/amd64.c
===================================================================
--- kernel/arch/amd64/src/amd64.c	(revision b1696194837e19c7e4d446880d20ede25043bad4)
+++ kernel/arch/amd64/src/amd64.c	(revision e4cc2660086726ebabd608e31dc30bc295305e1a)
@@ -60,4 +60,5 @@
 #include <arch/vreg.h>
 #include <arch/kseg.h>
+#include <arch/mm/pat.h>
 #include <genarch/pic/pic_ops.h>
 
@@ -115,4 +116,8 @@
 	/* Disable alignment check */
 	write_cr0(read_cr0() & ~CR0_AM);
+
+	/* Use PCD+PWT bit combination in PTE to mean write-combining mode. */
+	if (pat_supported())
+		pat_set_mapping(false, true, true, PAT_TYPE_WRITE_COMBINING);
 
 	if (config.cpu_active == 1) {