[meta-intel] [PATCH 1/1] README: Documentation of hardware features

[Kamble, Nitin A]

On 10/3/14, 7:26 AM, "Zanussi, Tom" <tom.zanussi at intel.com> wrote:

>On Thu, 2014-10-02 at 14:14 -0700, nitin.a.kamble at intel.com wrote:
>> From: Nitin A Kamble <nitin.a.kamble at intel.com>
>> 
>> 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 <nitin.a.kamble at intel.com>
>> ---
>>  README | 75 
>>++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 75 insertions(+)
>> 
>> diff --git a/README b/README
>> index c829fdb..f633f36 100644
>> --- a/README
>> +++ b/README
>> @@ -83,3 +83,78 @@ 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_SIGNATURES
>> +     variable. A sequence of iucode-tool parameters are listed in the
>> +     UCODE_FILTER_SIGNATURES 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
>> +
>
>I took a quick look at the iucode-tool manpage, but didn't see anything
>describing the signatures themselves or where to find them.  It would be
>helpful to the user of this feature to have some idea of where to look
>to find them.  Could you perhaps add a bit about that?

Sure, this would help.

Nitin

>
>Thanks,
>
>Tom
>
>> +  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.
>> +
>
>