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



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layer, since it is obsolete and just gets in the way.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.

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