Thanks for the patch, there are some minor style/cleanups that
could be done.
 

 #if defined(RTE_ARCH_X86)

Isn't this going to apply to 64 bit only?

+/*
+ * Try to detect whether the system uses 5-level page table.
+ */
+static bool
+system_uses_PML5(void)
+{
+	void *page_4k, *mask = (void *)0xf0000000000000;

Magic constants expressed like this seem wrong. Why not use
shift to make it obvious.

Also, you are assuming a particular layout of memory on
Linux which might be problematic. Plus if there is already
some memory in use there, it won't work.

+	page_4k = mmap(mask, 4096, PROT_READ | PROT_WRITE,
+		MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);

Since you are probing maybe MAP_FIXED is what you want.

+
+	if (page_4k == (void *) -1)
+		return false;

Use MMAP_FAILED here.

+	munmap(page_4k, 4096);
+
+	if ((unsigned long)page_4k & (unsigned long)mask)
+		return true;
+	return false;

Wouldn't this work the same for what you expect?
	return page_4k == mask;

I.e you expect kernel to put page where you want.