Re: [Xen-devel] [PATCH v1] libxl: Make an ACPI support build for ARM64 configurable.

[Julien Grall <julien.grall@xxxxxxx>]

On 23/11/16 15:47, Andrii Anisov wrote:
> Hello Julien,
Hi Andrii,

> > The ACPI support is pretty much contained in a single file and I am not sure 
> > you will win much space.
> > Can you explain why the ACPI guest support should be optional?
> This would increase the system configurability and would let one
> shrink a system to a minimal footprint with required functionality
> only. Such possibility is very useful in embedded applications.
>
> Unfortunately I don't know the exact space impact of this particular
> feature 'cause I can't build it. From other hand I do not need it in
> my system. So I would like to have a way to drop not needed
> functionality easily.
I agree with this argument however...

> BTW, excessive functionality reduction is also a way to get more
> stable and predictable system.
this statement is not entirely true. There is no automatic test on all 
the possible configurations, although we have travis to test build (and 
not booting) a random Kconfig. Even if we try our best to see any 
problem when reviewing code, we cannot guarantee an error when using a 
different configuration.
And this is becoming a problem as today we have no way to know the 
configuration used when a problem is reported. This is because the 
Kconfig is not embedded in the Xen binary.
I got bitten quite a few times in my development because I had a binary 
but not the Kconfig. It was re-written because I forgot to add 
XEN_CONFIG_EXPERT on the command line.
I might be more inclined to make more feature optional when we will have 
a way to track the configuration of a hypervisor binary.
Regards,

--
Julien Grall

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