From 527bf129f9a780e11b251cf2467dc30118a57d16 Mon Sep 17 00:00:00 2001 From: Yinghai Lu Date: Mon, 12 Aug 2013 16:43:24 -0700 Subject: [PATCH] x86/mm: Fix boot crash with DEBUG_PAGE_ALLOC=y and more than 512G RAM Dave Hansen reported that systems between 500G and 600G RAM crash early if DEBUG_PAGEALLOC is selected. > [ 0.000000] init_memory_mapping: [mem 0x00000000-0x000fffff] > [ 0.000000] [mem 0x00000000-0x000fffff] page 4k > [ 0.000000] BRK [0x02086000, 0x02086fff] PGTABLE > [ 0.000000] BRK [0x02087000, 0x02087fff] PGTABLE > [ 0.000000] BRK [0x02088000, 0x02088fff] PGTABLE > [ 0.000000] init_memory_mapping: [mem 0xe80ee00000-0xe80effffff] > [ 0.000000] [mem 0xe80ee00000-0xe80effffff] page 4k > [ 0.000000] BRK [0x02089000, 0x02089fff] PGTABLE > [ 0.000000] BRK [0x0208a000, 0x0208afff] PGTABLE > [ 0.000000] Kernel panic - not syncing: alloc_low_page: ran out of memory It turns out that we missed increasing needed pages in BRK to mapping initial 2M and [0,1M) when we switched to use the #PF handler to set memory mappings: > commit 8170e6bed465b4b0c7687f93e9948aca4358a33b > Author: H. Peter Anvin > Date: Thu Jan 24 12:19:52 2013 -0800 > > x86, 64bit: Use a #PF handler to materialize early mappings on demand Before that, we had the maping from [0,512M) in head_64.S, and we can spare two pages [0-1M). After that change, we can not reuse pages anymore. When we have more than 512M ram, we need an extra page for pgd page with [512G, 1024g). Increase pages in BRK for page table to solve the boot crash. Reported-by: Dave Hansen Bisected-by: Dave Hansen Tested-by: Dave Hansen Signed-off-by: Yinghai Lu Cc: # v3.9 and later Link: http://lkml.kernel.org/r/1376351004-4015-1-git-send-email-yinghai@kernel.org Signed-off-by: Ingo Molnar --- arch/x86/mm/init.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c index 2ec29ac78ae6b7..04664cdb7fda3d 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -78,8 +78,8 @@ __ref void *alloc_low_pages(unsigned int num) return __va(pfn << PAGE_SHIFT); } -/* need 4 4k for initial PMD_SIZE, 4k for 0-ISA_END_ADDRESS */ -#define INIT_PGT_BUF_SIZE (5 * PAGE_SIZE) +/* need 3 4k for initial PMD_SIZE, 3 4k for 0-ISA_END_ADDRESS */ +#define INIT_PGT_BUF_SIZE (6 * PAGE_SIZE) RESERVE_BRK(early_pgt_alloc, INIT_PGT_BUF_SIZE); void __init early_alloc_pgt_buf(void) {