Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755038Ab3DGFyh (ORCPT ); Sun, 7 Apr 2013 01:54:37 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:46375 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751332Ab3DGFyg (ORCPT ); Sun, 7 Apr 2013 01:54:36 -0400 Message-ID: <51610A25.4010301@oracle.com> Date: Sun, 07 Apr 2013 13:54:45 +0800 From: Zhenzhong Duan Reply-To: zhenzhong.duan@oracle.com Organization: oracle User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:17.0) Gecko/20130328 Thunderbird/17.0.5 MIME-Version: 1.0 To: "linux-kernel@vger.kernel.org" , xen-devel , Konrad Rzeszutek Wilk CC: Feng Jin , Tamon Shiose Subject: [PATCH-v2] xen: Don't call arch_trigger_all_cpu_backtrace in dom0(pvm) Content-Type: text/plain; charset=GB2312 Content-Transfer-Encoding: 7bit X-Source-IP: acsinet21.oracle.com [141.146.126.237] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2730 Lines: 72 nmi isn't supported in dom0, fallback to general all cpu backtrace code. Without fix, on xAPIC system, doing sysrq+l, no backtrace is showed, as xen_send_IPI_all is called and it doesn't support nmi vector. On x2APIC enabled system, got NULL pointer dereference as below. SysRq : Show backtrace of all active CPUs BUG: unable to handle kernel NULL pointer dereference at (null) IP: [] memcpy+0xb/0x120 Call Trace: [] ? __x2apic_send_IPI_mask+0x73/0x160 [] x2apic_send_IPI_all+0x1e/0x20 [] arch_trigger_all_cpu_backtrace+0x6c/0xb0 [] ? _raw_spin_lock_irqsave+0x34/0x50 [] sysrq_handle_showallcpus+0xe/0x10 [] __handle_sysrq+0x7d/0x140 [] ? __handle_sysrq+0x140/0x140 [] write_sysrq_trigger+0x57/0x60 [] proc_reg_write+0x86/0xc0 [] vfs_write+0xce/0x190 [] sys_write+0x55/0x90 [] system_call_fastpath+0x16/0x1b That's because apic points to apic_x2apic_cluster or apic_x2apic_phys but the basic element like cpumask isn't initialized. -v2: Mask x2APIC feature in pvm to avoid overwrite of apic pointer, update commit message per Konrad's suggestion. Signed-off-by: Zhenzhong Duan Tested-by: Tamon Shiose --- arch/x86/xen/enlighten.c | 3 +++ include/linux/nmi.h | 2 ++ 2 files changed, 5 insertions(+), 0 deletions(-) diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index c8e1c7b..12b0718 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -386,6 +386,9 @@ static void __init xen_init_cpuid_mask(void) cpuid_leaf1_edx_mask &= ~((1 << X86_FEATURE_APIC) | /* disable local APIC */ (1 << X86_FEATURE_ACPI)); /* disable ACPI */ + + cpuid_leaf1_ecx_mask &= ~(1 << (X86_FEATURE_X2APIC % 32)); + ax = 1; cx = 0; xen_cpuid(&ax, &bx, &cx, &dx); diff --git a/include/linux/nmi.h b/include/linux/nmi.h index db50840..b845757 100644 --- a/include/linux/nmi.h +++ b/include/linux/nmi.h @@ -32,6 +32,8 @@ static inline void touch_nmi_watchdog(void) #ifdef arch_trigger_all_cpu_backtrace static inline bool trigger_all_cpu_backtrace(void) { + if (xen_domain()) + return false; arch_trigger_all_cpu_backtrace(); return true; -- 1.7.3 -- 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/