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Date: Sat, 18 Aug 2012 01:15:19 -0700 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 01/11] Documentation/x86: Early load microcode From: Fenghua Yu <fenghua.yu@...el.com> Documenation for early load microcode methodology. Signed-off-by: Fenghua Yu <fenghua.yu@...el.com> --- 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 <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 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@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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