Re: [Xen-devel] QEMU build breakage on ARM against Xen 4.9 caused by libxendevicemodel

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 3 May 2017, Stefano Stabellini wrote:
> On Wed, 3 May 2017, Anthony PERARD wrote:
> > On Wed, May 03, 2017 at 10:20:59AM -0700, Stefano Stabellini wrote:
> > > On Wed, 3 May 2017, Anthony PERARD wrote:
> > > > On Thu, Apr 20, 2017 at 11:05:33AM -0700, Stefano Stabellini wrote:
> > > > > On Thu, 20 Apr 2017, Paul Durrant wrote:
> > > > > > I think xencall should be part of the base xen_stable_libs anyway.
> > > > > 
> > > > > Yes, you are right. However I noticed that -lxencall needs to come 
> > > > > after
> > > > > -lxendevicemodel. So, I'll have to move -lxendevicemodel before
> > > > > $xen_stable_libs, see below. I'll merge this patch into "configure:
> > > > > detect presence of libxendevicemodel", if that's OK.
> > > > > 
> > > > > diff --git a/configure b/configure
> > > > > index 99d6cbc..3133ef8 100755
> > > > > --- a/configure
> > > > > +++ b/configure
> > > > > @@ -1992,7 +1992,7 @@ if test "$xen" != "no" ; then
> > > > >    else
> > > > >  
> > > > >      xen_libs="-lxenstore -lxenctrl -lxenguest"
> > > > > -    xen_stable_libs="-lxenforeignmemory -lxengnttab -lxenevtchn"
> > > > > +    xen_stable_libs="-lxencall -lxenforeignmemory -lxengnttab 
> > > > > -lxenevtchn"
> > > > >  
> > > > >      # First we test whether Xen headers and libraries are available.
> > > > >      # If no, we are done and there is no Xen support.
> > > > > @@ -2027,9 +2027,9 @@ int main(void) {
> > > > >    return 0;
> > > > >  }
> > > > >  EOF
> > > > > -        compile_prog "" "$xen_libs $xen_stable_libs -lxendevicemodel"
> > > > > +        compile_prog "" "$xen_libs -lxendevicemodel $xen_stable_libs"
> > > > >        then
> > > > > -      xen_stable_libs="$xen_stable_libs -lxendevicemodel"
> > > > > +      xen_stable_libs="-lxendevicemodel $xen_stable_libs"
> > > > >        xen_ctrl_version=40900
> > > > >        xen=yes
> > > > >      elif
> > > > 
> > > > Hey, now that this patch is merged, xen.git fail to build QEMU. (osstest
> > > > qemu-mainline branch fail.)
> > > > 
> > > > That's because -lxencall is not found because -L$path_to_libxencall is
> > > > missing in xen.git.
> > > > 
> > > > But I've notice something else, libxendevicemodel.so is not linked
> > > > against libxencall, that might be the root of the issues on arm.
> > > > (libxenctrl.so is linked against libxencall.)
> > > > 
> > > > Thought?
> > > > 
> > > > 
> > > > We probably need this patch in xen:
> > > 
> > > We also need to add -L$path_to_libxencall and -I$path_to_libxencall to
> > > tools/Makefile:subdir-all-qemu-xen-dir.
> > 
> > I don't think that needed because:
> > for -I, QEMU does not use anything from xencall, and any other includes
> > does not use xencall.h.
> > 
> > for -L, I think that would be usefull only if QEMU is built staticly.
> > 
> > Also, I don't think -lxencall is needed at all, if libxendevicemodel is
> > fixed. libxencall will only be a runtime dependency.
> 
> I tried the patch below: on ARM, if I remove -L$DIR/tools/libs/call, the
> QEMU configure script detects Xen 4.7 instead of 4.9. If I also remove
> -Wl,-rpath-link=$DIR/tools/libs/call, it cannot detect Xen at all.
> 
> You are right that we can avoid -I and -l, but I think we need both -L
> and -Wl,-rpath-link for tools/libs/call.

Correction: the need for -L$DIR/tools/libs/call comes from -lxencall in
the QEMU configure script. If I remove -lxencall from configure, then it
works OK without it (as it should). But
-Wl,-rpath-link=$DIR/tools/libs/call is still required, otherwise the
xencall library cannot be found and loaded.


> > > > diff --git a/tools/libs/devicemodel/Makefile 
> > > > b/tools/libs/devicemodel/Makefile
> > > > index 55626a5049..81fa5a4ac4 100644
> > > > --- a/tools/libs/devicemodel/Makefile
> > > > +++ b/tools/libs/devicemodel/Makefile
> > > > @@ -63,7 +63,7 @@ libxendevicemodel.so.$(MAJOR): 
> > > > libxendevicemodel.so.$(MAJOR).$(MINOR)
> > > >         $(SYMLINK_SHLIB) $< $@
> > > >  
> > > >  libxendevicemodel.so.$(MAJOR).$(MINOR): $(PIC_OBJS) 
> > > > libxendevicemodel.map
> > > > -       $(CC) $(LDFLAGS) $(PTHREAD_LDFLAGS) -Wl,$(SONAME_LDFLAG) 
> > > > -Wl,libxendevicemodel.so.$(MAJOR) $(SHLIB_LDFLAGS) -o $@ $(PIC_OBJS) 
> > > > $(LDLIBS_libxentoollog) $(APPEND_LDFLAGS)
> > > > +       $(CC) $(LDFLAGS) $(PTHREAD_LDFLAGS) -Wl,$(SONAME_LDFLAG) 
> > > > -Wl,libxendevicemodel.so.$(MAJOR) $(SHLIB_LDFLAGS) -o $@ $(PIC_OBJS) 
> > > > $(LDLIBS_libxentoollog) $(LDLIBS_libxencall) $(APPEND_LDFLAGS)
> > > >  
> > > >  .PHONY: install
> > > >  install: build
> > > > 
> > > > -- 
> > > > Anthony PERARD
> > > > 
> > 
> > -- 
> > Anthony PERARD
> > 
> 

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