Re: [Qemu-devel] [PATCH 2/2] configure: use pkg-config for obtaining xen version

[Paul Durrant <Paul.Durrant@citrix.com>]

> -----Original Message-----
> From: Paul Durrant
> Sent: 24 March 2017 15:13
> To: 'Stefano Stabellini' <sstabellini@kernel.org>; Juergen Gross
> <jgross@suse.com>
> Cc: qemu-devel@nongnu.org; xen-devel@lists.xenproject.org; Anthony
> Perard <anthony.perard@citrix.com>; kraxel@redhat.com
> Subject: RE: [PATCH 2/2] configure: use pkg-config for obtaining xen version
> 
> > -----Original Message-----
> > From: Stefano Stabellini [mailto:sstabellini@kernel.org]
> > Sent: 22 March 2017 18:22
> > To: Juergen Gross <jgross@suse.com>
> > Cc: Stefano Stabellini <sstabellini@kernel.org>; qemu-devel@nongnu.org;
> > xen-devel@lists.xenproject.org; Anthony Perard
> > <anthony.perard@citrix.com>; kraxel@redhat.com; Paul Durrant
> > <Paul.Durrant@citrix.com>
> > Subject: Re: [PATCH 2/2] configure: use pkg-config for obtaining xen
> version
> >
> > On Wed, 22 Mar 2017, Juergen Gross wrote:
> > > On 21/03/17 19:54, Stefano Stabellini wrote:
> > > > On Tue, 21 Mar 2017, Juergen Gross wrote:
> > > >> On 17/03/17 19:33, Stefano Stabellini wrote:
> > > >>> On Fri, 17 Mar 2017, Juergen Gross wrote:
> > > >>>> On 16/03/17 21:20, Stefano Stabellini wrote:
> > > >>>>> On Thu, 16 Mar 2017, Juergen Gross wrote:
> > > >>>>>> Instead of trying to guess the Xen version to use by compiling
> > various
> > > >>>>>> test programs first just ask the system via pkg-config. Only if it
> > > >>>>>> can't return the version fall back to the test program scheme.
> > > >>>>>
> > > >>>>> That's OK, but why did you remove the Xen unstable test?
> > > >>>>
> > > >>>> >From Xen 4.9 on pkg-config will return the needed information.
> > There is
> > > >>>> no longer a need for a test program to determine the Xen version.
> > After
> > > >>>> all this was the main objective of my series adding the pkg-config
> > > >>>> files to Xen.
> > > >>>
> > > >>> I was going to say something like "yeah, but is pkg-config always
> > > >>> available?" In reality, QEMU already has pkg-config as build
> > > >>> dependency, so I guess there is no problem with that.
> > > >>>
> > > >>> Please add a note about this to the commit message.
> > > >>>
> > > >>
> > > >> Okay.
> > > >
> > > > Sorry to point this out only now, and I realize that it might be
> > > > unimportant for production builds, but it is important to me, and
> > > > developers in general, to be able to test a single QEMU tree against a
> > > > number of Xen trees (all releases from 4.3 onward).
> > > >
> > > > With this change (specifically dropping the 4.9 build test), out of tree
> > > > builds don't work anymore. I would like to be able to do:
> > > >
> > > > ./configure --enable-xen --target-list=i386-softmmu \
> > > >                 --extra-cflags="-I$DIR/tools/include \
> > > >                 -I$DIR/tools/libs/toollog/include \
> > > >                 -I$DIR/tools/libs/evtchn/include \
> > > >                 -I$DIR/tools/libs/gnttab/include \
> > > >                 -I$DIR/tools/libs/foreignmemory/include \
> > > >                 -I$DIR/tools/libs/devicemodel/include \
> > > >                 -I$DIR/tools/libxc/include \
> > > >                 -I$DIR/tools/xenstore/include \
> > > >                 -I$DIR/tools/xenstore/compat/include" \
> > > >                 --extra-ldflags="-L$DIR/tools/libxc \
> > > >                 -L$DIR/tools/xenstore \
> > > >                 -L$DIR/tools/libs/evtchn \
> > > >                 -L$DIR/tools/libs/gnttab \
> > > >                 -L$DIR/tools/libs/foreignmemory \
> > > >                 -L$DIR/tools/libs/devicemodel \
> > > >                 -Wl,-rpath-link=$DIR/tools/libs/toollog \
> > > >                 -Wl,-rpath-link=$DIR/tools/libs/evtchn \
> > > >                 -Wl,-rpath-link=$DIR/tools/libs/gnttab \
> > > >                 -Wl,-rpath-link=$DIR/tools/libs/call \
> > > >                 -Wl,-rpath-link=$DIR/tools/libs/foreignmemory \
> > > >                 -Wl,-rpath-link=$DIR/tools/libs/devicemodel" \
> > > >             --disable-kvm
> > > > make
> > > >
> > > > And the make should succeed. Is there a way to do that with pkg-
> config?
> > >
> > > Sure, for Xen 4.9 just do:
> > >
> > > PKG_CONFIG_PATH=$(DIR)/tools/pkg-config ./configure \
> > > 		--enable-xen --target-list=i386-softmmu \
> > > 		--disable-kvm
> > > make
> >
> > Yes, that works, thanks! I committed it to my next branch adding
> > "pkg-config, which is already a build dependency of QEMU, will be used
> > exclusively to determine the Xen version from Xen 4.9 onward." to the
> > commit message.
> 
> A further question...
> 
> I have a xen tree which I've been using to build and install master against my
> own checked out QEMU repo. No problem with that. I've now reverted my
> tree to 4.7.0 and cannot build tools (even after a make distclean) because
> QEMU's configure is still getting up a xen_ctrl_version of 40900. This is
> because pkg-config is still finding a 4.9.0 xencontrol package? Where is it
> getting this from?
> 

Even in a completely fresh checkout of xen.git RELEASE-4.7.2 tag I'm *still* getting a xen_ctrl_version of 40900, which presumably means it is coming from the version of xenctrl I have *installed* rather than the one I've built. This is quite a change in behaviour and one that is going to cause problems.

  Paul

>   Paul