From: Nitin A Kamble <[email protected]> Starting a new documentation section to describe the layer specific hardware features. At this point the intel-ucode machine feature is described here. In the future more such features will be described in this section.
Signed-off-by: Nitin A Kamble <[email protected]> --- README | 95 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 95 insertions(+) diff --git a/README b/README index c829fdb..66b6789 100644 --- a/README +++ b/README @@ -83,3 +83,98 @@ The meta-intel maintainers will do their best to review and/or pull in a patch or patchset within 24 hours of the time it was posted. For larger and/or more involved patches and patchsets, the review process may take longer. + + +Machine Features in the meta-intel layer +======================================== + +Many machine features are available in the oecore/poky layer for BSP use. +The meta-intel layer makes some additional machine features available for BSPs +using the meta-intel layer. + +Requirements +------------ + +The additional machine features are only available when the meta-intel layer +is included in the build config, and the meta-intel.inc file is included in +the machine configuration of the interested BSP. + +To make these features available for your machine, you will need to: + +1. have a configuration line as seen below in the bblayers.conf + BBLAYERS += "<local path>/meta-intel.git" +2. have the following line in the machine configuration + require conf/machine/include/meta-intel.inc + +Once the above requirements are met, then the machine features provided by +the meta-intel layer will be available for the BSP use. + +Available Machine Features +-------------------------- + +As of now the meta-intel layer provides the following list of machine features. +In the future, more machine features may be available in this list. + +* intel-ucode + +These machine features can be included by listing them in the MACHINE_FEATURES +variable in the machine configuration file. + +Details of the Machine Features +------------------------------- + +* intel-ucode: This feature provides microcode updating support for Intel + processors. With the intel-ucode feature, images get complete support for + updating the microcode on Intel processors. This feature enables microcode + updating at early boot time by placing the microcode data files in the + initrd image. It also puts the user land microcode updating tool iucode_tool + and the microcode data file in the target images. + + Q. Why to enable this microcode feature? + A. Intel releases microcode updates to correct processor behavior as + documented in the respective processor specification updates. While + the regular approach to getting this microcode update is via a BIOS + upgrade, this can be an administrative hassle and not always possible + in the field. The intel-ucode feature enables the microcode update + capability from the Linux OS. It provides an easy path for upgrading + processor microcode without need of changing BIOS. Once the feature + is enabled, it is also possible to update the existing images with + newer microcode update in the future. + + Q. How to bundle only specific microcodes in the target image? + A. The Intel microcode data file released by Intel contains microcode + updates for multiple processors. If the BSP image will be running only + on a certain kind of processors, then the number of microcodes bundled in + the target image can be filtered by specifying the UCODE_FILTER_PARAMETERS + variable. A sequence of iucode-tool parameters are listed in the + UCODE_FILTER_PARAMETERS variable to filter the microcodes from the + microcode data file. For more information on these parameters refer to + the iucode-tool manual page, which can be seen over here: + http://manned.org/iucode-tool + + Q. How to define the UCODE_FILTER_PARAMETERS variable for a BSP? + A. If the BSP image will be run only on specific processors, then the + microcode data can be filtered to take only the microcode updates + relevant to the processors of interest. To define the + UCODE_FILTER_PARAMETERS variable, one needs to find out the cpuid + signatures of all the processors the BSP can run on. An easy way to + find the cpuid signature of the board processors is to build and run + a microcode enabled image on the target hardware, without first + assigning any value to the UCODE_FILTER_PARAMETERS variable. Once + the image is booted, then run the "ucode_tool -S" command to scan the + system for processor signatures. It prints cpuid signatures for the + processors in the system. These signatures can then be used in the + UCODE_FILTER_PARAMETERS variable, to select the microcodes with -s + parameter. + Example: + [root@fri2 ~]# iucode_tool -S + iucode_tool: system has processor(s) with signature 0x00020661 + + Define UCODE_FILTER_PARAMETERS in the machine configuration as: + UCODE_FILTER_PARAMETERS = "-s 0x00020661" + + Q. When to not enable this microcode feature? + A. The microcode datafile and the associated tools take small (few KB) + space on the target image. The BSPs which are highly sensitive to the + target image size, which are not experiencing any microcode related issues, + may consider not enabling this feature to save the target image foot print. -- 1.8.1.4 -- _______________________________________________ meta-intel mailing list [email protected] https://lists.yoctoproject.org/listinfo/meta-intel
