x86: update populate_extra_pte() and add populate_extra_pmd()

Impact: minor change to populate_extra_pte() and addition of pmd flavor

Update populate_extra_pte() to return pointer to the pte_t for the
specified address and add populate_extra_pmd() which only populates
till the pmd and returns pointer to the pmd entry for the address.

For 64bit, pud/pmd/pte fill functions are separated out from
set_pte_vaddr[_pud]() and used for set_pte_vaddr[_pud]() and
populate_extra_{pte|pmd}().

Signed-off-by: Tejun Heo <tj@kernel.org>

arch/x86/kernel/setup_percpu.c

@@ -41,6 +41,11 @@ unsigned long __per_cpu_offset[NR_CPUS] __read_mostly = {
 };
 EXPORT_SYMBOL(__per_cpu_offset);
 
+static void __init pcpu4k_populate_pte(unsigned long addr)
+{
+	populate_extra_pte(addr);
+}
+
 static inline void setup_percpu_segment(int cpu)
 {
 #ifdef CONFIG_X86_32
@@ -104,7 +109,7 @@ void __init setup_per_cpu_areas(void)
 		}
 	}
 
-	pcpu_unit_size = pcpu_setup_static(populate_extra_pte, pages, size);
+	pcpu_unit_size = pcpu_setup_static(pcpu4k_populate_pte, pages, size);
 
 	free_bootmem(__pa(pages), pages_size);