[Libguestfs] [PATCH 1/2] mllib: add normalize_arch helper

[Pino Toscano]

On Tuesday 11 August 2015 15:05:04 Richard W.M. Jones wrote:
> On Tue, Aug 11, 2015 at 03:45:11PM +0200, Pino Toscano wrote:
> > Small helper to normalize an architecture string, so it is easier to
> > compare them and check for compatibilities.
> > 
> > Make use of it in guest_arch_compatible, simplifying it.
> 
> Have a look at:
> 8864c47b94cf44ac2d0d8d4b5019073ad1da121b

Yes, this is what patch #2 partially reverts (and it's mentioned
there).

> >  mllib/common_utils.ml  | 12 ++++++++++--
> >  mllib/common_utils.mli |  5 +++++
> >  2 files changed, 15 insertions(+), 2 deletions(-)
> > 
> > diff --git a/mllib/common_utils.ml b/mllib/common_utils.ml
> > index f9e8996..ca6d470 100644
> > --- a/mllib/common_utils.ml
> > +++ b/mllib/common_utils.ml
> > @@ -730,13 +730,21 @@ let rec mkdir_p path permissions =
> >      mkdir_p (Filename.dirname path) permissions;
> >      Unix.mkdir path permissions
> >  
> > +let normalize_arch = function
> > +  | "i386" | "i486" | "i586" | "i686" -> "i386"
> > +  | "amd64" | "x86_64" -> "x86_64"
> 
> Commit 8864c47b had "x64" also (added by you in b1cf6246).

IIRC x64 was for 64bit Windows guests, but for now that is not needed.

> > +  | "powerpc" | "ppc" -> "ppc"
> > +  | arch -> arch
> > +
> >  (* Are guest arch and host_cpu compatible, in terms of being able
> >   * to run commands in the libguestfs appliance?
> >   *)
> >  let guest_arch_compatible guest_arch =
> > -  match Config.host_cpu, guest_arch with
> > +  let own = normalize_arch Config.host_cpu in
> > +  let guest_arch = normalize_arch guest_arch in
> > +  match own, guest_arch with
> >    | x, y when x = y -> true
> > -  | "x86_64", ("i386"|"i486"|"i586"|"i686") -> true
> > +  | "x86_64", "i386" -> true
> >    | _ -> false
> 
> Commit 8864c47b may have got this wrong.  You cannot, for example, run
> 'dnf install' in an i686 guest, as it tries to install x86_64
> packages.  Try this command for example:
> 
>   virt-builder --arch i686 fedora-22 --install net-tools
> 
> There doesn't seem to be a way to force dnf to use another basearch.

I would say that this is not a problem of guest_arch_compatible itself
(running programs is possible as it is supposed to be), but more like
some dnf behaviour.  Maybe we should pass the architecture when
installing using yum/dnf and the appliance and guest architecture are
not the same?

> I wonder also if instead of a normalize function, we want a compare
> function.  Or maybe we want both?  A compare function is safer, maybe,
> since it preserves the actual arch string.

I guess it depends on how it is used. In the way patch #2 uses it in
virt-builder, the target architecture does not need to be preserved
exactly -- it is used only for checking among the templates, whose
architecture is normalized on the fly when searching, not changing what
is the actual value coming from the index.

Thanks,
-- 
Pino Toscano
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