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Re: [Xen-devel] POSIX error names and codes in PV protocols



Hi,

On 26/01/2017 17:28, Oleksandr Andrushchenko wrote:
On 01/26/2017 05:44 PM, Jan Beulich wrote:
On 26.01.17 at 15:40, <andr2000@xxxxxxxxx> wrote:
There is some work happening on new PV protocols: sndif [1],

displif [2], PV calls [3] and the common part of those is that

error/status codes must be returned as a part of a response packet.

For that Konrad suggested [1] (and Stefano already used in [3]) POSIX

to be employed here instead of defining protocol specific error codes.

The problem I see here is that POSIX only defines names of the errors,

but not values [4]. So, in order to use POSIX one still needs to define

the values (names must be the same, but values may differ for different
OSes).

So, the question is what would be the best option to

a) have those numbers defined in OS agnostic way

b) have those defined for all PV protocols

Stefano has already defined the error code values in his work [3],

but for other protocols this should be reimplemented again.
Aren't these simply what public/errno.h provides? Why would any
Xen specific protocol want to define their own, now that we have
this base set?

Jan
Indeed, thank you
The problem is that it is not exposed to Linux, but I can see it
in FreeBSD [1] and the helper to convert error codes [2] there as well.
Is there any reason these are not available in Linux?

This is because Linux and Xen are using the exact same error codes. The one in FreeBSD differs a bit, hence the helper to convert errors.

Strictly speaking Linux should have a converter, but it is not necessary today.

Cheers,

--
Julien Grall

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