Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754246Ab2HRIb5 (ORCPT ); Sat, 18 Aug 2012 04:31:57 -0400 Received: from mga02.intel.com ([134.134.136.20]:4511 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751673Ab2HRI3z (ORCPT ); Sat, 18 Aug 2012 04:29:55 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.77,790,1336374000"; d="scan'208";a="182264740" From: "Fenghua Yu" To: "H Peter Anvin" , "Ingo Molnar" , "Thomas Gleixner" , "Asit K Mallick" , "Tigran Aivazian" , "Andreas Herrmann" , "Borislav Petkov" , "linux-kernel" , "x86" Cc: "Fenghua Yu" Subject: [PATCH 01/11] Documentation/x86: Early load microcode Date: Sat, 18 Aug 2012 01:15:19 -0700 Message-Id: <1345277729-8399-2-git-send-email-fenghua.yu@intel.com> X-Mailer: git-send-email 1.7.2 In-Reply-To: <1345277729-8399-1-git-send-email-fenghua.yu@intel.com> References: <1345277729-8399-1-git-send-email-fenghua.yu@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2594 Lines: 67 From: Fenghua Yu Documenation for early load microcode methodology. Signed-off-by: Fenghua Yu --- Documentation/x86/earlyucode.txt | 43 ++++++++++++++++++++++++++++++++++++++ 1 files changed, 43 insertions(+), 0 deletions(-) create mode 100644 Documentation/x86/earlyucode.txt diff --git a/Documentation/x86/earlyucode.txt b/Documentation/x86/earlyucode.txt new file mode 100644 index 0000000..d8966d6 --- /dev/null +++ b/Documentation/x86/earlyucode.txt @@ -0,0 +1,43 @@ +Early load microcode +==================== +By Fenghua Yu + +Kernel can update microcode in early phase of boot time. Loading microcode early +can fix CPU issues before they are observed during kernel boot time. + +Microcode is stored in initrd file. The microcode is read from the initrd file +and loaded to CPU's during boot time. + +The format of the combined initrd image is microcode in cpio format followed by +initrd image (maybe compressed). Kernel parses the combined initrd image during +boot time. The microcode file in cpio name space is: +kernel/x86/microcode/GenuineIntel/microcode.hex + +During BSP boot (before SMP starts), if kernel finds the microcode file in the +initrd file, it parses the microcode and saves matching microcode in memory. +If matching microcode is found, it will be uploaded in BSP and later on in all +AP's. + +The saved microcode in memory will be used to upload micorcode when system +resumes from sleep. + +In the past, user can issue command to load microcode during run time. There are +two user space interfaces to load microcode, either through /dev/cpu/microcode +interface or through reload file in sysfs. + +Now user can choose any of the three methods to update microcode during boot +time or later during run time. + +The following sample script shows how to generate a new combined initrd file in +/boot/initrd-3.5.0.ucode.img with original microcode microcode.hex and +original initrd image /boot/initrd-3.5.0.img. + +mkdir initrd +cd initrd +cp ../microcode.hex kernel/x86/microcode/GenuineIntel/microcode.hex +find .|cpio -oc >../ucode.cpio +cd .. +cat ucode.cpio /boot/initrd-3.5.0.img >/boot/initrd-3.5.0.ucode.img + +The generated /boot/initrd-3.5.0.ucode.img can be used as initrd file to load +microcode during early boot time. -- 1.7.2 -- 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/