Re: [QUESTION] Minimal Xen Configuration

["Kwon, Gihwan" <gihwan.kwon@xxxxxxxxxx>]

Stefano, Nicola

> On Wed, 2 Apr 2025, Nicola Vetrini wrote:
>> On 2025-03-28 07:43, Kwon, Gihwan wrote:
>>> Dear Xen Community,
>>> 
>>> I hope this message finds you well.
>>> 
>>> I have heard that there exists a minimal Xen configuration optimized
>>> for safety-critical products, particularly in automotive applications,
>>> with the code size reduced to approximately 50k SLOC.
>>> 
>>> Could anyone provide guidance or point me to relevant resources
>>> regarding this minimal Xen configuration? Any insights or references
>>> would be greatly appreciated.
>>> 
>>> Thank you in advance for your assistance.
>>> 
>>> Best regards,
>>> Gihwan Kwon
>> 
>> Hello,
>> 
>> I am part of the team that provides static analysis for Xen, mainly
>> towards the objective to make Xen compliant with MISRA C guidelines. As
>> part of that effort, a minimal Xen configuration has been defined (for
>> Arm and x86_64) at [1], which is the one currently analyzed for static
>> analysis for each commit [2]. It starts from the default configuration
>> for the architecture (i.e., make defconfig) and then turns on or off
>> various Kconfig options, as specified by EXTRA_XEN_CONFIG.
>> 
>> @Stefano Stabellini (Cc'ed) is the main driving force behind the Xen
>> certification effort for automotive, therefore he's probably the best
>> person to approach to get more information on this matter.
> 
> Thanks Nicola. In addition to what Nicola wrote, there is an outstanding
> activity to further reduce the code size by adding more kconfig options.
> There are a couple of patch series on the list right now to that effect.
> 
> https://marc.info/?l=xen-devel&m=173745442831026
> 
> Last year we ran some experiments and for ARM we should be able to go
> below 35K LOC. The tools measuring LOC are very imprecise as they do not
> account for #ifdefs and kconfig options. So we switched to text binary
> size for measurements as it is more accurate. do not account for kconfig
> options and #ifdefs. Hence, we switch to using text size as size
> measurement for Xen. One of the figure was XXX.

Thank you for sharing information regarding the current minimal config
and additional activities. I have reviewed the configuration applied to the
 CI and have a question.
 
Currently, `CONFIG_SCHED_RTDS` is enabled instead of `CONFIG_SCHED_CREDIT2`
and `CONFIG_SCHED_CREDIT`. Is this because ARINC653 scheduler cannot be
used as default scheduler, as well as, rt scheduler is smaller than 
credit2 or credit scheduler?

- Gihwan