Messages in this thread | | | Date | Mon, 20 Aug 2012 14:26:00 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH 01/11] Documentation/x86: Early load microcode |
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On Sat, Aug 18, 2012 at 01:15:19AM -0700, Fenghua Yu wrote: > From: Fenghua Yu <fenghua.yu@intel.com> > > Documenation for early load microcode methodology. > > Signed-off-by: Fenghua Yu <fenghua.yu@intel.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
Let's call the doc file "early-microcode.txt" like the rest of the microcode-related files in the tree.
> @@ -0,0 +1,43 @@ > +Early load microcode > +==================== > +By Fenghua Yu <fenghua.yu@intel.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 ^ an
> +and loaded to CPU's during boot time.
I think you mean the plural "CPUs" here.
> + > +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 ^ the
> +boot time. The microcode file in cpio name space is:
Here and below, can we call the microcode file the "microcode container" to differentiate from the other "file" types?
s/time//
> +kernel/x86/microcode/GenuineIntel/microcode.hex > + > +During BSP boot (before SMP starts), if kernel finds the microcode file in the ^ the
> +initrd file, it parses the microcode and saves matching microcode in memory.
s/the microcode/it/
> +If matching microcode is found, it will be uploaded in BSP and later on in all
I guess "uploaded to the BSP" is more fitting here...
> +AP's.
APs.
> + > +The saved microcode in memory will be used to upload micorcode when system > +resumes from sleep.
Simplify:
"The cached microcode patch is applied when the CPU resumes from a sleep state."
> + > +In the past, user can issue command to load microcode during run time.
Delete that sentence, it is not needed.
> +There are two user space interfaces to load microcode, either through > +/dev/cpu/microcode interface or through reload file in sysfs.
s/interface//
"... or through /sys/devices/system/cpu/microcode/reload."
> + > +Now user can choose any of the three methods to update microcode during boot > +time or later during run time.
That sounds strange, maybe say something like:
"In addition to those two, the early loading method described here is the third method with which microcode can be uploaded to a system's CPUs."
> + > +The following sample script shows how to generate a new combined initrd file in
s/sample/example/
> +/boot/initrd-3.5.0.ucode.img with original microcode microcode.hex and ^ in
> +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 ^ an
> +microcode during early boot time.
Thanks.
-- Regards/Gruss, Boris.
Advanced Micro Devices GmbH Einsteinring 24, 85609 Dornach GM: Alberto Bozzo Reg: Dornach, Landkreis Muenchen HRB Nr. 43632 WEEE Registernr: 129 19551
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