Re: [Xen-devel] [PATCH v3 for-next 0/4] xen: Convert __page_to_mfn and _mfn_to_page to use typesafe MFN

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 06.11.17 at 12:47, <julien.grall@xxxxxxxxxx> wrote:
> Hi Jan,
> 
> On 06/11/17 11:37, Jan Beulich wrote:
>>>>> On 01.11.17 at 15:03, <julien.grall@xxxxxxxxxx> wrote:
>>> Most of the users of page_to_mfn and mfn_to_page are either overriding
>>> the macros to make them work with mfn_t or use mfn_x/_mfn becaue the rest
>>> of the function use mfn_t.
>>>
>>> So I think it is time to make __page_to_mfn and __mfn_to_page using typesafe
>>> MFN.
>> 
>> I have to admit that I still find the overall goal confusing: Afaict
>> the double-underscore-prefixed versions exist only to allow
>> easily overriding the non-prefixed ones. Hence the first and
>> foremost goal ought to be to convert everyone to using the
>> non-prefixed versions. Files wanting to avoid the typed forms
>> could then continue to use / be switched to the prefixed ones.
>> 
>> What you're doing here is producing a mess: The prefixed
>> versions should never have been touched in the first place.
>> And iirc this was discussed before, with the suggestion to use
>> overrides (for the non-prefixed versions) to limit overall patch
>> size.
> 
> At the end of the discussion in the previous version, you were happy 
> with the modification done here (see [1]).

From the angle looked at it back then I indeed was, but I'm looking
at this from a slightly different angle now with the reply above.

> Overall, I think this is an improvement compare to what we have today. 
> Because we enforce the use of MFN typesafe by default. The developer 
> would have to override the helpers if he wants to to use the 
> non-typesafe version.
> 
> With your suggestion here, you would just keep the override around even 
> when they are not necessary. They will have to be dropped at some point, 
> so why not now?

Why would we keep the overrides in place once no longer needed?
All I'm asking for is that the double-underscore prefixed macros be
left alone, and the non-prefixed versions be converted to be
type-safe by default (with the option to override). That'll allow the
prefixed variants to go way altogether once all code was switched
to typesafe, no longer requiring any overrides.

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel