Re: [Xen-devel] [PATCH for-4.6 2/3] libxl/psr: use Xen error codes when checking hypercall return values

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Ian Jackson writes ("Re: [PATCH for-4.6 2/3] libxl/psr: use Xen error codes 
when checking hypercall return values"):
> Acked-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>

Actually, I withdraw that.  I was confused about how things worked.
To summarise an irc discussion:

 * On NetBSD, hypercall numbers are translated by the privcmd driver.
   This is probably correct.  (Not sure if FreeBSD does the same.)

 * So the libxc API is that errno values are OS errno values.  Roger's
   patch is wrong.

 * A corrollary is that the hypervisor may not use errno values which
   are not in the toolstack OS.  Since the hypervisor is supposed to
   be fairly portable to different toolstacks, that means we shouldn't
   be using errno values which are not in POSIX.

 * Re EBADSLT in particular:
     - There is one return site in 4.5, which is in hvm_save_one,
       which is toolstack-onloy functionality.  We can therefore
       change it for 4.6.
     - The other sites where EBADSLT are generated in staging must
       also be fixed.

So the correct approach is:

 - Patch to change EBADSLT to something else, everywhere.
 - Patch to remove EBADSLT from hypervisor errno list (if it's not
   just been renamed/renumbered).
 - If FreeBSD privcmd does not translate errno numbers, make it do so.

Ian.

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