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Re: [PATCH RESEND 2/2] xen: Allow EXPERT mode to be selected from the menuconfig directly

Hi Jan,

On 30/04/2020 15:50, Jan Beulich wrote:
On 30.04.2020 16:25, Julien Grall wrote:
EXPERT mode is currently used to gate any options that are in technical
preview or not security supported At the moment, the only way to select
it is to use XEN_CONFIG_EXPERT=y on the make command line.

However, if the user forget to add the option of one of the make
command (even a clean), then .config will get rewritten. This may lead
to a rather frustrating experience as it is difficult to diagnostic the

Is / will this still be true after Anthony's rework of the build
system? Right now we already have

clean-targets := %clean
no-dot-config-targets := $(clean-targets) \

I haven't tried Anthony's rework yet. But I guess the problem would be the same if you forget to add XEN_CONFIG_EXPERT=y on make.

A lot of the options behind EXPERT would benefit to get more tested in
order to be mark as fully supported in the future.

Anyone intending to get an EXPERT-only option fully supported will
need to do focused testing; I don't think we can expect to move
items out of this category just because more people happen to test
something every now and then.

I didn't imply this was the only condition to get a feature security suported. I merely pointed out that more testing would help to harden the code. If you make difficult to access an option then it will be less tested and take longer to get it security supported.

In order to make easier to experiment, the option EXPERT can now be
selected from the menuconfig rather than make command line. This does
not change the fact a kernel with EXPERT mode selected will not be
security supported.

Well, if I'm not mis-remembering it was on purpose to make it more
difficult for people to declare themselves "experts". FAOD I'm not
meaning to imply I don't see and accept the frustration aspect you
mention further up. The two need to be carefully weighed against
one another.

Some of the options behind EXPERT mode don't make sense. For instance, how adding a built-in command line requires to be expert? I understand we don't want to support it, but I don't see any reason to make the user's life more difficult here.


Julien Grall



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