Re: [Xen-devel] [PATCH] x86: add a user configurable Kconfig option for the VGA

[Derek Straka <derek@xxxxxxxxxxx>]

On Tue, Sep 20, 2016 at 9:12 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:

>>> On 20.09.16 at 14:35, <derek@xxxxxxxxxxx> wrote:
> On Wed, Sep 14, 2016 at 6:47 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>
>> >>> On 13.09.16 at 21:40, <derek@xxxxxxxxxxx> wrote:
>> > Allows for the conditional inclusion of VGA driver on the x86 platform
>> > rather than having it always enabled.
>>
>> So I guess with all three of these patches an overview mail is missing.
>> What are you trying to accomplish? Solely reducing the binary size of
>> Xen doesn't seem like a very important goal to me, and eliminating
>> these drivers from the build doesn't appear to help make Xen more
>> stable of secure.
>>
> I agree with your assessment on the stability and security standpoint.  Our
> customer has asked us to remove
> unused drivers based on functionality of a set of boards.  Each of the
> boards has a subset of the available hardware functionality
> brought out to accessible headers.

Well, does that mean that's just to reduce the size of the hypervisor?
If so, I'm honestly not sure we want to set a precedent here, since
if we do, people could come and suggest to make all sorts of code
build conditionally, and I don't think our plans with Kconfig so far were
going in that direction (but others may disagree with me here).

For the most part: yes.  At the end of the day, my customer wants to reduce the size of hypervisor.  I disagree a bit that these specific changes 

would set a poor precedent of for configuration.  The reason I proposed it in the first place was the mechanisms for conditional compilation 

were already implicitly available via HAS_*.  I thought adding the ability for the user to explicitly define the configuration option

would be a permissible extension of the capability already present.  That said, I do see your point about limiting the scope of conditional 

code to avoid an eventual mess.  Thanks.

-Derek 

Jan

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