linux-kernel - [PATCH v2 01/10] Documentation/x86: Early load microcode

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1354240068-9821-2-git-send-email-fenghua.yu@intel.com>
Date:	Thu, 29 Nov 2012 17:47:39 -0800
From:	"Fenghua Yu" <fenghua.yu@...el.com>
To:	"H Peter Anvin" <hpa@...or.com>, "Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Asit K Mallick" <asit.k.mallick@...el.com>,
	"Tigran Aivazian" <tigran@...azian.fsnet.co.uk>,
	"Andreas Herrmann" <andreas.herrmann3@....com>,
	"Borislav Petkov" <borislav.petkov@....com>,
	"linux-kernel" <linux-kernel@...r.kernel.org>,
	"x86" <x86@...nel.org>
Cc:	"Fenghua Yu" <fenghua.yu@...el.com>
Subject: [PATCH v2 01/10] Documentation/x86: Early load microcode

From: Fenghua Yu <fenghua.yu@...el.com>

Documenation for early loading microcode methodology.

Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
---
 Documentation/x86/early-microcode.txt |   43 +++++++++++++++++++++++++++++++++
 1 files changed, 43 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/x86/early-microcode.txt

diff --git a/Documentation/x86/early-microcode.txt b/Documentation/x86/early-microcode.txt
new file mode 100644
index 0000000..9b3a6ab
--- /dev/null
+++ b/Documentation/x86/early-microcode.txt
@@ -0,0 +1,43 @@
+Early load microcode
+====================
+By Fenghua Yu <fenghua.yu@...el.com>
+
+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 an initrd file. The microcode is read from the initrd
+file and loaded to CPUs during boot time.
+
+The format of the combined initrd image is microcode in cpio format followed by
+the 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.bin
+
+During BSP boot (before SMP starts), if the 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
+APs.
+
+The cached microcode patch is applied when CPUs resume from a sleep state.
+
+There are two legacy user space interfaces to load microcode, either through
+/dev/cpu/microcode or through /sys/devices/system/cpu/microcode/reload file
+in sysfs.
+
+In addition to these two legacy methods, the early loading method described
+here is the third method with which microcode can be uploaded to a system's
+CPUs.
+
+The following example 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@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/