x86: update reference for PAE tlb flushing

Remove bogus reference to "Pentium-II erratum A13" and point to the
actual canonical source of information about what requirements x86
processors have for PAE pagetable updates.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/asm-x86/pgalloc_32.h

@@ -80,8 +80,10 @@ static inline void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmd)
 	set_pud(pudp, __pud(__pa(pmd) | _PAGE_PRESENT));
 
 	/*
-	 * Pentium-II erratum A13: in PAE mode we explicitly have to flush
-	 * the TLB via cr3 if the top-level pgd is changed...
+	 * According to Intel App note "TLBs, Paging-Structure Caches,
+	 * and Their Invalidation", April 2007, document 317080-001,
+	 * section 8.1: in PAE mode we explicitly have to flush the
+	 * TLB via cr3 if the top-level pgd is changed...
 	 */
 	if (mm == current->active_mm)
 		write_cr3(read_cr3());

include/asm-x86/pgtable-3level.h

@@ -98,8 +98,10 @@ static inline void pud_clear(pud_t *pudp)
 	set_pud(pudp, __pud(0));
 
 	/*
-	 * Pentium-II erratum A13: in PAE mode we explicitly have to flush
-	 * the TLB via cr3 if the top-level pgd is changed...
+	 * According to Intel App note "TLBs, Paging-Structure Caches,
+	 * and Their Invalidation", April 2007, document 317080-001,
+	 * section 8.1: in PAE mode we explicitly have to flush the
+	 * TLB via cr3 if the top-level pgd is changed...
 	 *
 	 * Make sure the pud entry we're updating is within the
 	 * current pgd to avoid unnecessary TLB flushes.