From: Dave Hansen With PAE on, there are only 4 PGD entries. The kernel ones never change, so there is no need to copy them when a vmalloc fault occurs. This was this was causing problems with the split pmd patches, but it is still correct for mainline. Tested with and without PAE. I ran it in a loop turning on and off 10 swap partitions, which is what excited the original bug. http://bugme.osdl.org/show_bug.cgi?id=640 25-akpm/arch/i386/mm/fault.c | 8 ++++++++ 1 files changed, 8 insertions(+) diff -puN arch/i386/mm/fault.c~dont-set-kernel-pgd-on-PAE arch/i386/mm/fault.c --- 25/arch/i386/mm/fault.c~dont-set-kernel-pgd-on-PAE Wed Apr 30 16:52:01 2003 +++ 25-akpm/arch/i386/mm/fault.c Wed Apr 30 16:52:01 2003 @@ -333,7 +333,15 @@ vmalloc_fault: if (!pgd_present(*pgd_k)) goto no_context; + /* + * kernel pmd pages are shared among all processes + * with PAE on. Since vmalloc pages are always + * in the kernel area, this will always be a + * waste with PAE on. + */ +#ifndef CONFIG_X86_PAE set_pgd(pgd, *pgd_k); +#endif pmd = pmd_offset(pgd, address); pmd_k = pmd_offset(pgd_k, address); _