diff --git a/arch/x86/mm/Makefile_32 b/arch/x86/mm/Makefile_32
index 6a5e981..be2f551 100644
--- a/arch/x86/mm/Makefile_32
+++ b/arch/x86/mm/Makefile_32
@@ -4,6 +4,7 @@
 
 obj-y	:= init_32.o pgtable_32.o fault_32.o ioremap_32.o extable.o pageattr_32.o mmap.o
 
+obj-$(CONFIG_CPA_DEBUG) += pageattr-test.o
 obj-$(CONFIG_NUMA) += discontig_32.o
 obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
 obj-$(CONFIG_HIGHMEM) += highmem_32.o
diff --git a/arch/x86/mm/Makefile_64 b/arch/x86/mm/Makefile_64
index 09c997f..cb72316 100644
--- a/arch/x86/mm/Makefile_64
+++ b/arch/x86/mm/Makefile_64
@@ -7,3 +7,4 @@
 obj-$(CONFIG_NUMA) += numa_64.o
 obj-$(CONFIG_K8_NUMA) += k8topology_64.o
 obj-$(CONFIG_ACPI_NUMA) += srat_64.o
+obj-$(CONFIG_CPA_DEBUG) += pageattr-test.o
diff --git a/arch/x86/mm/pageattr-test.c b/arch/x86/mm/pageattr-test.c
new file mode 100644
index 0000000..4b22eb4
--- /dev/null
+++ b/arch/x86/mm/pageattr-test.c
@@ -0,0 +1,233 @@
+/*
+ * self test for change_page_attr.
+ *
+ * Clears the global bit on random pages in the direct mapping, then reverts
+ * and compares page tables forwards and afterwards.
+ */
+
+#include <linux/mm.h>
+#include <linux/random.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/bootmem.h>
+#include <asm/cacheflush.h>
+#include <asm/pgtable.h>
+#include <asm/kdebug.h>
+
+enum {
+	NTEST = 400,
+#ifdef CONFIG_X86_64
+	LOWEST_LEVEL = 4,
+	LPS = (1 << PMD_SHIFT),
+#elif defined(CONFIG_X86_PAE)
+	LOWEST_LEVEL = 3,
+	LPS = (1 << PMD_SHIFT),
+#else
+	LOWEST_LEVEL = 3, /* lookup_address lies here */
+	LPS = (1 << 22),
+#endif
+	GPS = (1<<30)
+};
+
+#ifdef CONFIG_X86_64
+#include <asm/proto.h>
+#define max_mapped end_pfn_map
+#else
+#define max_mapped max_low_pfn
+#endif
+
+struct split_state {
+	long lpg, gpg, spg, exec;
+	long min_exec, max_exec;
+};
+
+static __init int print_split(struct split_state *s)
+{
+	int printed = 0;
+	long i, expected, missed = 0;
+	int err = 0;
+
+	s->lpg = s->gpg = s->spg = s->exec = 0;
+	s->min_exec = ~0UL;
+	s->max_exec = 0;
+	for (i = 0; i < max_mapped; ) {
+		int level;
+		pte_t *pte;
+		unsigned long adr = (unsigned long)__va(i << PAGE_SHIFT);
+
+		pte = lookup_address(adr, &level);
+		if (!pte) {
+			if (!printed) {
+				dump_pagetable(adr);
+				printk("CPA %lx no pte level %d\n", adr, level);
+				printed = 1;
+			}
+			missed++;
+			i++;
+			continue;
+		}
+
+		if (level == 2 && sizeof(long) == 8) {
+			s->gpg++;
+			i += GPS/PAGE_SIZE;
+		} else if (level != LOWEST_LEVEL) {
+			if (!(pte_val(*pte) & _PAGE_PSE)) {
+				printk("%lx level %d but not PSE %Lx\n",
+					adr, level, (u64)pte_val(*pte));
+				err = 1;
+			}
+			s->lpg++;
+			i += LPS/PAGE_SIZE;
+		} else {
+			s->spg++;
+			i++;
+		}
+		if (!(pte_val(*pte) & _PAGE_NX)) {
+			s->exec++;
+			if (adr < s->min_exec)
+				s->min_exec = adr;
+			if (adr > s->max_exec)
+				s->max_exec = adr;
+		}
+	}
+	printk("CPA mapping 4k %lu large %lu gb %lu x %lu[%lx-%lx] miss %lu\n",
+		s->spg, s->lpg, s->gpg, s->exec,
+		s->min_exec != ~0UL ? s->min_exec : 0, s->max_exec, missed);
+	expected = (s->gpg*GPS + s->lpg*LPS)/PAGE_SIZE + s->spg + missed;
+	if (expected != i) {
+		printk("CPA max_mapped %lu but expected %lu\n",
+			max_mapped, expected);
+		return 1;
+	}
+	return err;
+}
+
+static __init int state_same(struct split_state *a, struct split_state *b)
+{
+	return a->lpg == b->lpg && a->gpg == b->gpg && a->spg == b->spg &&
+			a->exec == b->exec;
+}
+
+static unsigned long addr[NTEST] __initdata;
+static unsigned len[NTEST] __initdata;
+
+/* Change the global bit on random pages in the direct mapping */
+static __init int exercise_pageattr(void)
+{
+	int i, k;
+	pte_t *pte, pte0;
+	int level;
+	int err;
+	struct split_state sa, sb, sc;
+	int failed = 0;
+	unsigned long *bm;
+
+	printk("CPA exercising pageattr\n");
+
+	bm = vmalloc((max_mapped + 7) / 8);
+	if (!bm) {
+		printk("CPA Cannot vmalloc bitmap\n");
+		return -ENOMEM;
+	}
+	memset(bm, 0, (max_mapped + 7) / 8);
+
+	failed += print_split(&sa);
+	srandom32(100);
+	for (i = 0; i < NTEST; i++) {
+		unsigned long pfn = random32() % max_mapped;
+		addr[i] = (unsigned long)__va(pfn << PAGE_SHIFT);
+		len[i] = random32() % 100;
+		len[i] = min_t(unsigned long, len[i], max_mapped - pfn - 1);
+		if (len[i] == 0)
+			len[i] = 1;
+
+		pte = NULL;
+		pte0 = pfn_pte(0, __pgprot(0)); /* shut gcc up */
+		for (k = 0; k < len[i]; k++) {
+			pte = lookup_address(addr[i] + k*PAGE_SIZE, &level);
+			if (!pte || pgprot_val(pte_pgprot(*pte)) == 0) {
+				addr[i] = 0;
+				break;
+			}
+			if (k == 0)
+				pte0 = *pte;
+			else if (pgprot_val(pte_pgprot(*pte)) !=
+					pgprot_val(pte_pgprot(pte0))) {
+				len[i] = k;
+				break;
+			}
+			if (test_bit(pfn + k, bm)) {
+				len[i] = k;
+				break;
+			}
+			__set_bit(pfn + k, bm);
+		}
+		if (!addr[i] || !pte || !k) {
+			addr[i] = 0;
+			continue;
+		}
+
+		err = change_page_attr(virt_to_page(addr[i]), len[i],
+			    pte_pgprot(pte_clrhuge(pte_clrglobal(pte0))));
+		if (err < 0) {
+			printk("CPA %d failed %d\n", i, err);
+			failed++;
+		}
+
+		pte = lookup_address(addr[i], &level);
+		if (!pte || pte_global(*pte) || pte_huge(*pte)) {
+			printk("CPA %lx: bad pte %Lx\n", addr[i],
+				pte ? (u64)pte_val(*pte) : 0ULL);
+			failed++;
+		}
+		if (level != LOWEST_LEVEL) {
+			printk("CPA %lx: unexpected level %d\n", addr[i],
+					level);
+			failed++;
+		}
+
+	}
+	vfree(bm);
+	global_flush_tlb();
+
+	failed += print_split(&sb);
+
+	printk("CPA reverting everything\n");
+	for (i = 0; i < NTEST; i++) {
+		if (!addr[i])
+			continue;
+		pte = lookup_address(addr[i], &level);
+		if (!pte) {
+			printk("CPA lookup of %lx failed\n", addr[i]);
+			failed++;
+			continue;
+		}
+		err = change_page_attr(virt_to_page(addr[i]), len[i],
+					  pte_pgprot(pte_mkglobal(*pte)));
+		if (err < 0) {
+			printk("CPA reverting failed: %d\n", err);
+			failed++;
+		}
+		pte = lookup_address(addr[i], &level);
+		if (!pte || !pte_global(*pte)) {
+			printk("CPA %lx: bad pte after revert %Lx\n", addr[i],
+			       pte ? (u64)pte_val(*pte) : 0ULL);
+			failed++;
+		}
+
+	}
+	global_flush_tlb();
+
+	failed += print_split(&sc);
+	if (!state_same(&sa, &sc))
+		failed++;
+
+	if (failed)
+		printk("CPA selftests NOT PASSED. Please report.\n");
+	else
+		printk("CPA selftests PASSED\n");
+
+	return 0;
+}
+
+module_init(exercise_pageattr);