x86: add periodic corruption check

Perodically check for corruption in low phusical memory.  Don't bother
checking at fault time, since it won't show anything useful.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/mm/fault.c

@@ -848,8 +848,6 @@ no_context:
  * Oops. The kernel tried to access some bad page. We'll have to
  * terminate things with extreme prejudice.
  */
-	check_for_bios_corruption();
-
 #ifdef CONFIG_X86_32
 	bust_spinlocks(1);
 #else

arch/x86/mm/init_32.c

@@ -907,6 +907,8 @@ void __init mem_init(void)
 	int codesize, reservedpages, datasize, initsize;
 	int tmp;
 
+	start_periodic_check_for_corruption();
+
 #ifdef CONFIG_FLATMEM
 	BUG_ON(!mem_map);
 #endif

arch/x86/mm/init_64.c

@@ -769,6 +769,8 @@ void __init mem_init(void)
 {
 	long codesize, reservedpages, datasize, initsize;
 
+	start_periodic_check_for_corruption();
+
 	pci_iommu_alloc();
 
 	/* clear_bss() already clear the empty_zero_page */