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

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Juergen Gross [mailto:jgross@xxxxxxxx]
> Sent: 24 March 2017 15:55
> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>; 'Stefano Stabellini'
> <sstabellini@xxxxxxxxxx>
> Cc: Anthony Perard <anthony.perard@xxxxxxxxxx>; xen-
> devel@xxxxxxxxxxxxxxxxxxxx; qemu-devel@xxxxxxxxxx; kraxel@xxxxxxxxxx
> Subject: Re: [Xen-devel] [PATCH 2/2] configure: use pkg-config for obtaining
> xen version
> 
> On 24/03/17 16:51, Juergen Gross wrote:
> > On 24/03/17 16:44, Paul Durrant wrote:
> >>> -----Original Message-----
> >>> From: Juergen Gross [mailto:jgross@xxxxxxxx]
> >>> Sent: 24 March 2017 15:35
> >>> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>; 'Stefano Stabellini'
> >>> <sstabellini@xxxxxxxxxx>
> >>> Cc: Anthony Perard <anthony.perard@xxxxxxxxxx>; xen-
> >>> devel@xxxxxxxxxxxxxxxxxxxx; qemu-devel@xxxxxxxxxx;
> kraxel@xxxxxxxxxx
> >>> Subject: Re: [Xen-devel] [PATCH 2/2] configure: use pkg-config for
> obtaining
> >>> xen version
> >>>
> >>> On 24/03/17 16:12, Paul Durrant wrote:
> >>>>> -----Original Message-----
> >>>>> From: Stefano Stabellini [mailto:sstabellini@xxxxxxxxxx]
> >>>>> Sent: 22 March 2017 18:22
> >>>>> To: Juergen Gross <jgross@xxxxxxxx>
> >>>>> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>; qemu-
> >>> devel@xxxxxxxxxx;
> >>>>> xen-devel@xxxxxxxxxxxxxxxxxxxx; Anthony Perard
> >>>>> <anthony.perard@xxxxxxxxxx>; kraxel@xxxxxxxxxx; Paul Durrant
> >>>>> <Paul.Durrant@xxxxxxxxxx>
> >>>>> 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?
> >>>
> >>> Hmm, could it be you have Xen unstable installed on your machine?
> >>
> >> I do indeed. I build on my test machine.
> >>
> >>>
> >>> Didn't think of this problem. I can think of 3 solutions:
> >>>
> >>> a) delete the xencontrol.pc file (on my system under
> >>>    /usr/share/pkgconfig/ )
> >>>
> >>
> >> I just found mine using pkg-config --debug... /usr/local/share/pkgconfig
> for me
> >>
> >>> b) we add a patch to qemu to test an environment variable whether
> >>>    pkg-config should be ignored for Xen version detection
> >>>
> >>> c) set the environment variable PKG_CONFIG_LIBDIR to a local directory
> >>>    and copy all but the xen*.pc files from /usr/share/pkgconfig/ (or
> >>>    your correct directory) to it (or link them to avoid missing updates)
> >>>
> >>> OTOH this is something you have to be aware of for other packages as
> >>> well: mixing the build environment and the target environment can lead
> >>> to bad results. Now Xen has been added to the list.
> >>>
> >>
> >> That's a change in behaviour that I, and probably others, have long been
> used to. What we really want, presumably, is to have pkg-config just look
> under tools/pkgconfig when querying for the version of xencontrol. Could
> that not be done by simply setting PKG_CONFIG_LIBDIR in QEMU's configure
> script, or would it still mean picking up installed libraries before ones just
> built?
> >
> > I guess this would break qemu's configure badly as it wouldn't find all
> > the other library informations it is looking for via pkg-config.
> 
> Aah, wait, you mean just for the Xen query?
> 

Yes, we want QEMU to pick up xen libs from the build env and not any that have 
been previously installed the default search path needs to be squashed.

> This might complicate things for my qemu stubdom plans...
> 

Maybe that can be worked around in the stubdom build?

  Paul

> 
> Juergen

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel