From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933278AbcI1Tec (ORCPT ); Wed, 28 Sep 2016 15:34:32 -0400 Received: from mail.kernel.org ([198.145.29.136]:36344 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932951AbcI1TeY (ORCPT ); Wed, 28 Sep 2016 15:34:24 -0400 From: Andy Lutomirski To: x86@kernel.org Cc: david@saggiorato.net, Borislav Petkov , Brian Gerst , linux-kernel@vger.kernel.org, Andy Lutomirski Subject: [PATCH 2/3] x86/boot: Fix another __read_cr4() case on 486 Date: Wed, 28 Sep 2016 12:34:15 -0700 Message-Id: <70dfb68f8f312764d5f6aca6e2aa6d7dc76df6e4.1475091074.git.luto@kernel.org> X-Mailer: git-send-email 2.7.4 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 The condition for reading CR4 was wrong: there are some CPUs with CPUID but not CR4. Rather than trying to make the condition exact, using __read_cr4_safe(). Reported-by: david@saggiorato.net Fixes: 18bc7bd523e0 ("x86/boot: Synchronize trampoline_cr4_features and mmu_cr4_features directly") Signed-off-by: Andy Lutomirski --- arch/x86/kernel/setup.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index 0fa60f5f5a16..5930a4d191b4 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -1137,9 +1137,13 @@ void __init setup_arch(char **cmdline_p) * auditing all the early-boot CR4 manipulation would be needed to * rule it out. */ - if (boot_cpu_data.cpuid_level >= 0) - /* A CPU has %cr4 if and only if it has CPUID. */ - mmu_cr4_features = __read_cr4(); + if (boot_cpu_data.cpuid_level >= 0) { + /* + * CPUs without CPUID don't have CR4. CPUs with CPUID + * usually have CR4. + */ + mmu_cr4_features = __read_cr4_safe(); + } memblock_set_current_limit(get_max_mapped()); -- 2.7.4