Re: [Xen-devel] [v5][PATCH 10/16] tools: introduce some new parameters to set rdm policy

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Chen, Tiejun writes ("Re: [v5][PATCH 10/16] tools: introduce some new 
parameters to set rdm policy"):
> [Ian Jackson:]
> > As I understand this feature, I don't think the name `type' is right.
> > This is a method for handling or overriding/ignoring the RDM problem.
> >
> > Perhaps `handling=' or `strategy=' ?
> 
> Okay, I prefer to use 'strategy='.

(We are discussing this on irc.)

> > And `none' seems quite an innocuous name for such a dangerous
> > setting.  How about `ignore' ?
...

[Later:]
> As I discussed with Campbell we'd like not to expose "none" in xl level 
> since this is equivalent to that case we don't set anything.

I think this observation of mine applies to the libxl API level too.


> >> Default per-device RDM policy is 'strict', while default global
> >> RDM policy is 'relaxed'. And the per-device policy would override
> >> the global policy like others.
> >
> > I don't think these two sentences can both be true.  If the per-device
> > policy overrides the global policy, then the per-device policy must
> > have at least three values: `strict', `relaxed', and `not set'
> > (implicitly using global policy).
> 
> Yeah. The per-device policy is first set as the global policy. This 
> behavior is same as other pci option. Please see the last patch,

OK, then can you please amend the commit message to be true :-).


> > This suggests that the default is "do the dangerous thing".  That
> > doesn't seem right.
> 
> As I discussed with Campbell we'd like not to expose "none" in xl level 
> since this is equivalent to that case we don't set anything.

That's not really an answer to what I have said, I think.

Why is the default the option that the documentation recommends to
avoid ?

> "none" means we have a chance to work as before since not all devices 
> own RDM. But as I said above this is same as !rdm.

Are we expecting many existing devices, and existing setups, to break
if we don't make the default be to ignore the problem ?

Ian.

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