On Sat, Aug 18, 2012 at 01:15:19AM -0700, Fenghua Yu wrote: > From: Fenghua Yu <fenghua...@intel.com> > > Documenation for early load microcode methodology. > > Signed-off-by: Fenghua Yu <fenghua...@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...@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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/