Re: [PATCH 1/2] xen/*/nospec: Provide common versions of evaluate_nospec/block_speculation

[Oleksii <oleksii.kurochko@xxxxxxxxx>]

On Tue, 2024-03-05 at 16:43 +0100, Jan Beulich wrote:
> On 05.03.2024 16:15, Oleksii wrote:
> > I agree that upon examining the current state of the code around
> > these
> > functions, it appears safe to provide stubs. However, the reason my
> > patch was rejected is that it may not be entirely safe, as Julien
> > pointed out that even with Arm, some functions shouldn't be empty.
> > 
> > What I would like to propose is that it might be beneficial, at
> > least
> > in CONFIG_DEBUG=y, to have a warning message. Does that make sense?
> 
> A warning message to what effect? And are you thinking of a build-
> time
> warning, or a runtime one? Plus wouldn't different aspects quickly
> lead
> to proliferation of warnings?
A warning message about that an empty definition is provided for
evaluate_nospec/block_speculation functions, so a developer will know
that it can be an issue.

Personally, I am OK with having this function empty by default as it is
done in the patch with opportunity to being redefined in arch specific
code if it is necessary, but I remembered that I had the similar
questions in my patch series which probably should be covered in this
patch series.

Runtime message can also be an option, but I thought about build-time,
but I agree that it can lead to proliferation of warning, so not the
best one idea.

~ Oleksii