RE: [QUESTION] Minimal Xen Configuration

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

Stefano and Nicola,

> 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?

Please disregard my previous message. I have double checked that 
mentioned configurations are set 'n'. Therefore,  `CONFIG_SCHED_NULL` 
and  `CONFIG_SCHED_CREDIT2` is being set and used in the minimal xen 
configuration.

> 
> - Gihwan
> 
>

- Gihwan