From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261209AbULWLVk (ORCPT ); Thu, 23 Dec 2004 06:21:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261210AbULWLVk (ORCPT ); Thu, 23 Dec 2004 06:21:40 -0500 Received: from e2.ny.us.ibm.com ([32.97.182.142]:32172 "EHLO e2.ny.us.ibm.com") by vger.kernel.org with ESMTP id S261209AbULWLVf (ORCPT ); Thu, 23 Dec 2004 06:21:35 -0500 Subject: [PATCH] Secondary cpus boot-up for non defalut location built kernels From: Vivek Goyal To: lkml Cc: fastboot , Linus Torvalds , Andrew Morton , "Eric W. Biederman" , dipankar sarma Content-Type: multipart/mixed; boundary="=-g3ER876ZvIFtdj5+5rrs" Organization: Message-Id: <1103802944.8123.114.camel@2fwv946.in.ibm.com> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.2.2 (1.2.2-5) Date: 23 Dec 2004 17:25:44 +0530 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org --=-g3ER876ZvIFtdj5+5rrs Content-Type: text/plain Content-Transfer-Encoding: 7bit Hi, This patch fixes the problem of secondary cpus boot up. This situation is faced when kernel is built for non default locations like 16MB and onwards. In this configuration, only primary cpu (BP) comes and secondary cpus don't boot. 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. This patch uses lgdtl instead of lgdt to force operand size to 32 instead of 16. Testing Details: ---------------- I have tested the patch on all combinations of following testing setup. Kernel: ------ 2.6.10-rc3-mm1 Hardware: --------- 1. 8way, PIII, 2. 4way, Xeon, Hyper Threaded Boot Loader: ----------- 1. Grub 2. LILO 3. Kexec Memory Location Kernel built for: -------------------------------- 1MB 32MB Kernel Image Type: ------------------ bzImage Thanks Vivek -- Vivek Goyal Linux Technology Center India Software Labs IBM India, Bangalore --=-g3ER876ZvIFtdj5+5rrs Content-Disposition: attachment; filename=boot_ap_for_nondefault_kernel.patch Content-Type: text/plain; name=boot_ap_for_nondefault_kernel.patch; charset=UTF-8 Content-Transfer-Encoding: 7bit This patch fixes the problem of secondary cpus not coming up over a reboot. This problem was seen when a kernel compiled for non default (16MB) location is booted. Signed-off-by: Vivek Goyal --- linux-2.6.10-rc3-mm1-changes-root/arch/i386/kernel/trampoline.S | 8 +++++++- 1 files changed, 7 insertions(+), 1 deletion(-) diff -puN arch/i386/kernel/trampoline.S~boot_ap_for_nondefault_kernel arch/i386/kernel/trampoline.S --- linux-2.6.10-rc3-mm1-changes/arch/i386/kernel/trampoline.S~boot_ap_for_nondefault_kernel 2004-12-22 16:36:50.000000000 +0530 +++ linux-2.6.10-rc3-mm1-changes-root/arch/i386/kernel/trampoline.S 2004-12-22 16:47:54.000000000 +0530 @@ -51,8 +51,14 @@ r_base = . movl $0xA5A5A5A5, trampoline_data - r_base # write marker for master knows we're running + /* 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. + */ + lidt boot_idt - r_base # load idt with 0, 0 - lgdt boot_gdt - r_base # load gdt with whatever is appropriate + lgdtl boot_gdt - r_base # load gdt with whatever is appropriate xor %ax, %ax inc %ax # protected mode (PE) bit _ --=-g3ER876ZvIFtdj5+5rrs--