From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752439AbbIQVLN (ORCPT ); Thu, 17 Sep 2015 17:11:13 -0400 Received: from mail.kernel.org ([198.145.29.136]:58507 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752141AbbIQVLJ (ORCPT ); Thu, 17 Sep 2015 17:11:09 -0400 From: Andy Lutomirski To: x86@kernel.org Cc: Paolo Bonzini , Peter Zijlstra , KVM list , Arjan van de Ven , xen-devel , linux-kernel@vger.kernel.org, Linus Torvalds , Andrew Morton , Ingo Molnar , Thomas Gleixner , Andy Lutomirski Subject: [PATCH 2/2] x86/msr: Set the return value to zero when native_rdmsr_safe fails Date: Thu, 17 Sep 2015 14:11:02 -0700 Message-Id: X-Mailer: git-send-email 2.4.3 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This will cause unchecked native_rdmsr_safe failures to return deterministic results. We could poison the results with something other than zero, but that would increase code size. Signed-off-by: Andy Lutomirski --- arch/x86/include/asm/msr.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h index 77d8b284e4a7..9eda52205d42 100644 --- a/arch/x86/include/asm/msr.h +++ b/arch/x86/include/asm/msr.h @@ -73,7 +73,10 @@ static inline unsigned long long native_read_msr_safe(unsigned int msr, asm volatile("2: rdmsr ; xor %[err],%[err]\n" "1:\n\t" ".section .fixup,\"ax\"\n\t" - "3: mov %[fault],%[err] ; jmp 1b\n\t" + "3: mov %[fault],%[err]\n\t" + "xorl %%eax, %%eax\n\t" + "xorl %%edx, %%edx\n\t" + "jmp 1b\n\t" ".previous\n\t" _ASM_EXTABLE(2b, 3b) : [err] "=r" (*err), EAX_EDX_RET(val, low, high) -- 2.4.3