From 983d5dbdb2b38d024935f560a91cddcf704875f3 Mon Sep 17 00:00:00 2001 From: Vivek Goyal Date: Thu, 12 Jan 2006 03:35:20 +0100 Subject: [PATCH] x86_64: Fix SMP bootup with CONFIG_KDUMP enabled o This fix was posted for i386 long back. Posting it for x86_64. http://marc.theaimsgroup.com/?l=linux-kernel&m=110380103229830&w=2 o This patch fixes the problem of secondary cpus boot up. This situation is faced when kernel is built for default locations like 16MB and onwards. In this configuration, only primary cpu (BP) comes and secondary cpus don't boot. o Problem occurs because in trampoline code, lgdt is not able to load the GDT as it happens to be situated beyond 16MB. This is due to the fact that cpu is still in real mode and default operand size is 16bit. o This patch uses lgdtl instead of lgdt to force operand size to 32 instead of 16. Signed-off-by: Vivek Goyal Signed-off-by: Andi Kleen Signed-off-by: Linus Torvalds --- arch/x86_64/kernel/trampoline.S | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/arch/x86_64/kernel/trampoline.S b/arch/x86_64/kernel/trampoline.S index 6d9c9a8e7d0..23a03eb91fc 100644 --- a/arch/x86_64/kernel/trampoline.S +++ b/arch/x86_64/kernel/trampoline.S @@ -42,8 +42,15 @@ r_base = . movl $0xA5A5A5A5, trampoline_data - r_base # write marker for master knows we're running - lidt idt_48 - r_base # load idt with 0, 0 - lgdt gdt_48 - r_base # load gdt with whatever is appropriate + /* + * GDT tables in non default location kernel can be beyond 16MB and + * lgdt will not be able to load the address as in real mode default + * operand size is 16bit. Use lgdtl instead to force operand size + * to 32 bit. + */ + + lidtl idt_48 - r_base # load idt with 0, 0 + lgdtl gdt_48 - r_base # load gdt with whatever is appropriate xor %ax, %ax inc %ax # protected mode (PE) bit -- cgit v1.2.3