From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752195Ab3LLX6F (ORCPT ); Thu, 12 Dec 2013 18:58:05 -0500 Received: from mga11.intel.com ([192.55.52.93]:11328 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752057Ab3LLX6C (ORCPT ); Thu, 12 Dec 2013 18:58:02 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.95,475,1384329600"; d="scan'208";a="449239743" From: Andi Kleen To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, Andi Kleen Subject: [PATCH 2/2] x86, microcode: Add option to allow downgrading of microcode Date: Thu, 12 Dec 2013 15:57:48 -0800 Message-Id: <1386892668-22256-2-git-send-email-andi@firstfloor.org> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1386892668-22256-1-git-send-email-andi@firstfloor.org> References: <1386892668-22256-1-git-send-email-andi@firstfloor.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andi Kleen For testing purposes it can be useful to downgrade microcode. Normally the driver only allows upgrading. Add a module_param (default off) that allows downgrading. Note the module_param can currently not be set for early ucode update, only for late. Signed-off-by: Andi Kleen --- arch/x86/kernel/microcode_intel_lib.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/x86/kernel/microcode_intel_lib.c b/arch/x86/kernel/microcode_intel_lib.c index ce69320..18d5325 100644 --- a/arch/x86/kernel/microcode_intel_lib.c +++ b/arch/x86/kernel/microcode_intel_lib.c @@ -26,11 +26,16 @@ #include #include #include +#include #include #include #include +static bool allow_downgrade; +module_param(allow_downgrade, bool, 0644); +MODULE_PARM_DESC(allow_downgrade, "Allow downgrading microcode"); + static inline int update_match_cpu(unsigned int csig, unsigned int cpf, unsigned int sig, unsigned int pf) @@ -41,6 +46,8 @@ update_match_cpu(unsigned int csig, unsigned int cpf, int update_match_revision(struct microcode_header_intel *mc_header, int rev) { + if (allow_downgrade) + return 1; return (mc_header->rev <= rev) ? 0 : 1; } -- 1.8.3.1