Re: [PATCH RFC 0/6+2+2] Begin to disentangle libxenctrl and provide some stable libraries

[Antti Kantee <pooka@iki.fi>]

On 10/06/15 16:15, Wei Liu wrote:
> On Wed, Jun 10, 2015 at 05:01:27PM +0100, Ian Jackson wrote:
>> Ian Campbell writes ("[PATCH RFC 0/6+2+2] Begin to disentangle libxenctrl and provide some stable libraries"):
>>> [stuff]
>>
>> Most of this looks good to me.
>>
>>> As part of this change I've begun to get rid of the osdep interface
>>> layer, since it is obsolete and just gets in the way. IIRC there were
>>> some tricks being played to use this on rumpkernels to mix and match
>>> facilities from xc_minios.c and xc_netbsd.c.
>>
>> Replacing those tricks with appropriate #ifdefs would be fine.
>>
>
> FYI I think I will write more glue code to make rump kernel to just use
> netbsd code, because they don't want to expose underlying minios
> functionalities to application level.

It's not so much that we outright "don't want to" as "prefer not to". 
If there's a strong reason, e.g. a measurably significant performance 
improvement, then we can talk.  However, anything calling past the libc 
interface is dipping into internal interfaces.  We make no guarantee 
about internal interface stability.

One good summary of 8 years of rump kernel development would be "lack of 
compartmentalization always comes back to bite you", so IMO it's better 
to conceptually maintain separation even where not enforced by a MMU and 
just make everything go through the guaranteed-stable syscall interfaces.