Fengguang Wu reported a BUG: Int 6: CR2 (null) on x86 platform in 0-day Linux Kernel Performance Test: [ 0.000000] BRK [0x025ee000, 0x025eefff] PGTABLE [ 0.000000] cma: dma_contiguous_reserve(limit 13ffe000) [ 0.000000] cma: dma_contiguous_reserve: reserving 31 MiB for global area [ 0.000000] BUG: Int 6: CR2 (null) [ 0.000000] EDI c0000000 ESI (null) EBP 41c11ea4 EBX 425cc101 [ 0.000000] ESP 41c11e98 ES 0000007b DS 0000007b [ 0.000000] EDX 00000001 ECX (null) EAX 41cd8150 [ 0.000000] vec 00000006 err (null) EIP 41072227 CS 00000060 flg 00210002 [ 0.000000] Stack: 425cc150 (null) (null) 41c11ef4 41d4ee4d (null) 13ffe000 41c11ec4 [ 0.000000] 41c2d900 (null) 13ffe000 (null) 4185793e 0000002e 410c2982 41c11f00 [ 0.000000] 410c2df5 (null) (null) (null) 425cc150 00013efe (null) 41c11f28 [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 3.17.0-next-20141008 #815 [ 0.000000] 00000000 425cc101 41c11e48 41850786 41c11ea4 41d2b1db 41d95f71 00000006 [ 0.000000] 00000000 c0000000 00000000 41c11ea4 425cc101 41c11e98 0000007b 0000007b [ 0.000000] 00000001 00000000 41cd8150 00000006 00000000 41072227 00000060 00210002 [ 0.000000] Call Trace: [ 0.000000] [<41850786>] dump_stack+0x16/0x18 [ 0.000000] [<41d2b1db>] early_idt_handler+0x6b/0x6b [ 0.000000] [<41072227>] ? __phys_addr+0x2e/0xca [ 0.000000] [<41d4ee4d>] cma_declare_contiguous+0x3c/0x2d7 [ 0.000000] [<4185793e>] ? _raw_spin_unlock_irqrestore+0x59/0x91 [ 0.000000] [<410c2982>] ? wake_up_klogd+0x8/0x33 [ 0.000000] [<410c2df5>] ? console_unlock+0x448/0x461 [ 0.000000] [<41d6d359>] dma_contiguous_reserve_area+0x27/0x47 [ 0.000000] [<41d6d4d1>] dma_contiguous_reserve+0x158/0x163 [ 0.000000] [<41d33e0f>] setup_arch+0x79b/0xc68 [ 0.000000] [<4184c0b4>] ? printk+0x1c/0x1e [ 0.000000] [<41d2b7cf>] start_kernel+0x9c/0x456 [ 0.000000] [<41d2b2ca>] i386_start_kernel+0x79/0x7d see detail: https://lkml.org/lkml/2014/10/8/708 It is because dma_contiguous_reserve() is called before initmem_init() in x86, the variable high_memory is not initialized but accessed by __pa(high_memory) in dma_contiguous_reserve(). This patch moves dma_contiguous_reserve() after initmem_init() so that high_memory is initialized before accessed. Reported-by: Fengguang Wu <fengguang.wu@xxxxxxxxx> Signed-off-by: Weijie Yang <weijie.yang@xxxxxxxxxxx> --- arch/x86/kernel/setup.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index 235cfd3..ab08aa2 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -1128,7 +1128,6 @@ void __init setup_arch(char **cmdline_p) setup_real_mode(); memblock_set_current_limit(get_max_mapped()); - dma_contiguous_reserve(max_pfn_mapped << PAGE_SHIFT); /* * NOTE: On x86-32, only from this point on, fixmaps are ready for use. @@ -1159,6 +1158,7 @@ void __init setup_arch(char **cmdline_p) early_acpi_boot_init(); initmem_init(); + dma_contiguous_reserve(max_pfn_mapped << PAGE_SHIFT); /* * Reserve memory for crash kernel after SRAT is parsed so that it -- 1.7.0.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>