Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755565AbYGGRa1 (ORCPT ); Mon, 7 Jul 2008 13:30:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753835AbYGGRaT (ORCPT ); Mon, 7 Jul 2008 13:30:19 -0400 Received: from mail.in-ulm.de ([217.10.8.10]:39861 "HELO mail.in-ulm.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753684AbYGGRaS (ORCPT ); Mon, 7 Jul 2008 13:30:18 -0400 X-Greylist: delayed 397 seconds by postgrey-1.27 at vger.kernel.org; Mon, 07 Jul 2008 13:30:17 EDT Date: Mon, 7 Jul 2008 19:23:34 +0200 From: Christian Ehrhardt To: linux-kernel@vger.kernel.org Subject: Boot failures on Qemu due to P6_NOPS Message-ID: <20080707172334.GH1009@lisa.in-ulm.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3170 Lines: 84 Hi, this might well be a bug in Qemu but even then, it would be nice if the linux kernel could do a work around. I tried to boot a current git kernel (around 2.6.26-rc8) on qemu and got the an invalid opcode oops on boot (full oops data below). The illegal instruction is 0x0f 0x1f 0x00 aka P6_NOP3. I have verified that this opcode gets patched in because apply_alternatives() or more precisely add_nops() uses P6 nops on this CPU type while padding after patching in an fxsave instruction. More precisely the code that oopses is: fxsave (%eax) btl $0x7,0x2(%eax) jae 0x804833e fnclex nopl (%eax) <==== Faulting instruction P6 nops are used when patching because init_intel() sets X86_FEATURE_P3 for family 6 CPUs and X86_FEATURE_P3 in turn enables the P6 NOPS. The Qemu CPU identifies itself as follows: processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 3 model name : Pentium II (Klamath) stepping : 3 cpu MHz : 1862.133 I have no idea if this specific CPU type should support this specific instruction. If it really should this is obviously a Qemu bug but it might be reasonable to work around this in the linux kernel. The kernel is configured with CONFIG_M586 but without CONFIG_X86_GENERIC (full config upon request). Apparently setting CONFIG_X86_GENERIC works around the problem. ========== ooops data follows =================================== invalid opcode: 0000 [#1] SMP Modules linked in: Pid: 0, comm: swapper Not tainted (2.6.26-rc9 #1) EIP: 0060:[] EFLAGS: 00000202 CPU: 0 EIP is at prepare_to_copy+0x1d/0x43 EAX: c781de00 EBX: 00000000 ECX: c03f3f9c EDX: c03c23e0 ESI: fffffff4 EDI: c03c23e0 EBP: 00000000 ESP: c03f3f08 DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 Process swapper (pid: 0, ti=c03f2000 task=c03c23e0 task.ti=c03f2000) Stack: c011c653 c03f3f9c 00000000 00800b00 00000286 00000000 00000000 00000000 00800b00 c03f3f9c 00000000 c011d671 00000000 00000000 00000000 00000000 c03c8cb0 00000246 c03c8a80 00000046 00000000 00000002 00000001 c014a30c Call Trace: [] copy_process+0x70/0xf75 [] do_fork+0xab/0x19c [] free_pages_bulk+0x23/0x1d0 [] native_sched_clock+0x90/0xa4 [] kernel_init+0x0/0x25d [] kernel_thread+0x78/0x80 [] kernel_init+0x0/0x25d [] kernel_thread_helper+0x0/0x10 [] rest_init+0x11/0x4b [] start_kernel+0x2a0/0x2a3 ======================= Code: ff 05 0c 20 47 c0 c3 ff 0d 0c 20 47 c0 c3 89 c2 8b 40 04 f6 40 0c 01 74 30 8b 82 6c 02 00 00 0f ae 00 0f ba 60 02 07 73 02 db e2 <0f> 1f 00 90 8d b4 26 00 00 00 00 89 f6 8b 42 04 83 60 0c fe 0f EIP: [] prepare_to_copy+0x1d/0x43 SS:ESP 0068:c03f3f08 ---[ end trace 4eaa2a86a8e2da22 ]--- Kernel panic - not syncing: Attempted to kill the idle task! regards Christian -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/