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Re: [PATCH v2] docs: specify stability of hypfs path documentation

On 16.07.20 13:24, Jan Beulich wrote:
On 16.07.2020 12:31, Jürgen Groß wrote:
On 16.07.20 12:11, Jan Beulich wrote:
On 15.07.2020 16:37, George Dunlap wrote:
IT sounds like you’re saying:

1. Paths listed without conditions will always be available

2. Paths listed with conditions may be extended: i.e., a node currently listed 
as PV might also become available for HVM guests

3. Paths listed with conditions might have those conditions reduced, but will never 
entirely disappear.  So something currently listed as PV might be reduced to 
CONFIG_HAS_FOO, but won’t be completely removed.

Is that what you meant?

I see Jürgen replied "yes" to this, but I'm not sure about 1.
above: I think it's quite reasonable to expect that paths without
condition may gain a condition. Just like paths now having a
condition and (perhaps temporarily) losing it shouldn't all of
the sudden become "always available" when they weren't meant to

As far a 3. goes, I'm also unsure in how far this is any better
stability wise (from a consumer pov) than allowing paths to
entirely disappear.

The idea is that any user tool using hypfs can rely on paths under 1 to
exist, while the ones under 3 might not be there due to the hypervisor
config or the used system.

A path not being allowed to entirely disappear ensures that it remains
in the documentation, so the same path can't be reused for something
different in future.

And then how do you deal with a condition getting dropped, and
later wanting to get re-added? Do we need a placeholder condition
like [ALWAYS] or [TRUE]?

Dropping a condition has to be considered very carefully, same as
introducing a new path without any condition.

In worst case you can still go with [CONFIG_HYPFS].




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