Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753196AbaFML0k (ORCPT ); Fri, 13 Jun 2014 07:26:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51847 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751044AbaFML0j (ORCPT ); Fri, 13 Jun 2014 07:26:39 -0400 From: Vitaly Kuznetsov To: Konrad Rzeszutek Wilk , Boris Ostrovsky , David Vrabel Cc: x86@kernel.org, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, Andrew Jones Subject: [PATCH] xenpv: don't BUG when failing to setup NMI callback Date: Fri, 13 Jun 2014 13:26:28 +0200 Message-Id: <1402658788-24477-1-git-send-email-vkuznets@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org some old Xen hypervisors (prior to 3.2) forbid DomUs to register NMI callbacks. E.g. we have the following code in xen-3.1: if ( (d->domain_id != 0) || (v->vcpu_id != 0) ) return -EINVAL; Commit 6efa20e49b9cb1db1ab66870cc37323474a75a13 introduced kernel crash in case PV guest fails to register NMI callback. All x86_64 PV guests will fail to boot on top of such hypervisors (RHEL5 example): (XEN) traps.c:405:d7 Unhandled invalid opcode fault/trap [#6] in domain 7 on VCPU 0 [ec=0000] (XEN) domain_crash_sync called from entry.S (XEN) Domain 7 (vcpu#0) crashed on cpu#3: (XEN) ----[ Xen-3.1.2-389.el5 x86_64 debug=n Not tainted ]---- (XEN) CPU: 3 (XEN) RIP: e033:[] (XEN) RFLAGS: 0000000000000282 CONTEXT: guest (XEN) rax: ffffffffffffffea rbx: 0000000000000000 rcx: 0000000000000002 (XEN) rdx: 0000000000000001 rsi: ffffffff81b0fe28 rdi: 0000000000000000 (XEN) rbp: ffffffff81b0fe40 rsp: ffffffff81b0fde8 r8: 0000000000000000 (XEN) r9: ffffffff81b0fdd0 r10: 0000000000007ff0 r11: 00000000ffffffff (XEN) r12: ffffffff81d65900 r13: 0000000000000000 r14: 0000000000000000 (XEN) r15: 0000000000000000 cr0: 0000000080050033 cr4: 00000000000026b0 (XEN) cr3: 000000013a263000 cr2: 0000000000000000 (XEN) ds: 0000 es: 0000 fs: 0000 gs: 0000 ss: e02b cs: e033 ... However it is possible to proceed without NMI callback registered. Change BUG() with warning in case of -EINVAL. Signed-off-by: Vitaly Kuznetsov --- arch/x86/xen/setup.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c index 821a11a..5b8b180 100644 --- a/arch/x86/xen/setup.c +++ b/arch/x86/xen/setup.c @@ -593,8 +593,17 @@ void xen_enable_syscall(void) void xen_enable_nmi(void) { #ifdef CONFIG_X86_64 - if (register_callback(CALLBACKTYPE_nmi, (char *)nmi)) + int ret; + + ret = register_callback(CALLBACKTYPE_nmi, (char *)nmi); + if (ret == -EINVAL) { + /* Hypervisor probably forbids us to register NMI callback, + that is expected when running on top of Xen-3.1 and older */ + pr_warn("xen: failed to register NMI callback\n"); + } else if (ret != 0) { + /* Other hypervisor failure */ BUG(); + } #endif } void __init xen_pvmmu_arch_setup(void) -- 1.9.3 -- 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/