From 4b239f458c229de044d6905c2b0f9fe16ed9e01e Mon Sep 17 00:00:00 2001 From: Yinghai Lu Date: Fri, 17 Dec 2010 16:58:28 -0800 Subject: [PATCH] x86-64, mm: Put early page table high While dubug kdump, found current kernel will have problem with crashkernel=512M. It turns out that initial mapping is to 512M, and later initial mapping to 4G (acutally is 2040M in my platform), will put page table near 512M. then initial mapping to 128g will be near 2g. before this patch: [ 0.000000] initial memory mapped : 0 - 20000000 [ 0.000000] init_memory_mapping: [0x00000000000000-0x0000007f74ffff] [ 0.000000] 0000000000 - 007f600000 page 2M [ 0.000000] 007f600000 - 007f750000 page 4k [ 0.000000] kernel direct mapping tables up to 7f750000 @ [0x1fffc000-0x1fffffff] [ 0.000000] memblock_x86_reserve_range: [0x1fffc000-0x1fffdfff] PGTABLE [ 0.000000] init_memory_mapping: [0x00000100000000-0x0000207fffffff] [ 0.000000] 0100000000 - 2080000000 page 2M [ 0.000000] kernel direct mapping tables up to 2080000000 @ [0x7bc01000-0x7bc83fff] [ 0.000000] memblock_x86_reserve_range: [0x7bc01000-0x7bc7efff] PGTABLE [ 0.000000] RAMDISK: 7bc84000 - 7f745000 [ 0.000000] crashkernel reservation failed - No suitable area found. after patch: [ 0.000000] initial memory mapped : 0 - 20000000 [ 0.000000] init_memory_mapping: [0x00000000000000-0x0000007f74ffff] [ 0.000000] 0000000000 - 007f600000 page 2M [ 0.000000] 007f600000 - 007f750000 page 4k [ 0.000000] kernel direct mapping tables up to 7f750000 @ [0x7f74c000-0x7f74ffff] [ 0.000000] memblock_x86_reserve_range: [0x7f74c000-0x7f74dfff] PGTABLE [ 0.000000] init_memory_mapping: [0x00000100000000-0x0000207fffffff] [ 0.000000] 0100000000 - 2080000000 page 2M [ 0.000000] kernel direct mapping tables up to 2080000000 @ [0x207ff7d000-0x207fffffff] [ 0.000000] memblock_x86_reserve_range: [0x207ff7d000-0x207fffafff] PGTABLE [ 0.000000] RAMDISK: 7bc84000 - 7f745000 [ 0.000000] memblock_x86_reserve_range: [0x17000000-0x36ffffff] CRASH KERNEL [ 0.000000] Reserving 512MB of memory at 368MB for crashkernel (System RAM: 133120MB) It means with the patch, page table for [0, 2g) will need 2g, instead of under 512M, page table for [4g, 128g) will be near 128g, instead of under 2g. That would good, if we have lots of memory above 4g, like 1024g, or 2048g or 16T, will not put related page table under 2g. that would be have chance to fill the under 2g if 1G or 2M page is not used. the code change will use add map_low_page() and update unmap_low_page() for 64bit, and use them to get access the corresponding high memory for page table setting. Signed-off-by: Yinghai Lu LKML-Reference: <4D0C0734.7060900@kernel.org> Signed-off-by: H. Peter Anvin --- arch/x86/mm/init.c | 9 +++---- arch/x86/mm/init_64.c | 63 +++++++++++++++++++------------------------ 2 files changed, 30 insertions(+), 42 deletions(-) diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c index c0e28a13de7d..5863950ebe0c 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -33,7 +33,7 @@ int direct_gbpages static void __init find_early_table_space(unsigned long end, int use_pse, int use_gbpages) { - unsigned long puds, pmds, ptes, tables, start; + unsigned long puds, pmds, ptes, tables, start = 0, good_end = end; phys_addr_t base; puds = (end + PUD_SIZE - 1) >> PUD_SHIFT; @@ -73,12 +73,9 @@ static void __init find_early_table_space(unsigned long end, int use_pse, * need roughly 0.5KB per GB. */ #ifdef CONFIG_X86_32 - start = 0x7000; -#else - start = 0x8000; + good_end = max_pfn_mapped << PAGE_SHIFT; #endif - base = memblock_find_in_range(start, max_pfn_mapped<