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

[Stefano Stabellini]

On Wed, 19 Apr 2017, Paul Durrant wrote:
> > -----Original Message-----
> > From: Stefano Stabellini [mailto:address@hidden
> > Sent: 18 April 2017 18:41
> > To: Paul Durrant <address@hidden>
> > Cc: 'Stefano Stabellini' <address@hidden>; address@hidden;
> > Anthony Perard <address@hidden>; Wei Liu
> > <address@hidden>; address@hidden; address@hidden; xen-
> > address@hidden
> > Subject: RE: QEMU build breakage on ARM against Xen 4.9 caused by
> > libxendevicemodel
> > 
> > On Tue, 18 Apr 2017, Paul Durrant wrote:
> > > > -----Original Message-----
> > > > From: Stefano Stabellini [mailto:address@hidden
> > > > Sent: 15 April 2017 01:40
> > > > To: Stefano Stabellini <address@hidden>
> > > > Cc: Paul Durrant <address@hidden>; address@hidden;
> > > > Anthony Perard <address@hidden>; Wei Liu
> > > > <address@hidden>; address@hidden; address@hidden; xen-
> > > > address@hidden
> > > > Subject: Re: QEMU build breakage on ARM against Xen 4.9 caused by
> > > > libxendevicemodel
> > > >
> > > > On Fri, 14 Apr 2017, Stefano Stabellini wrote:
> > > > > Hi Paul,
> > > > >
> > > > > The following commit in my qemu "next" branch breaks the build on
> > arm
> > > > > and arm64:
> > > > >
> > > > > commit 670271647ad15e9d937ced7a72c892349c709216
> > > > > Author: Paul Durrant <address@hidden>
> > > > > Date:   Tue Mar 7 10:55:34 2017 +0000
> > > > >
> > > > >     xen: use libxendevicemodel when available
> > > > >
> > > > > See the appended build log. Sorry for not realizing it sooner.
> > > >
> > > > As I imagined, this bug is easy to solve. It is reproducible on x86 too,
> > > > if you pass -DXC_WANT_COMPAT_DEVICEMODEL_API=1 to configure
> > and
> > > > forcefully disable Xen 4.9 detection in the configure script.
> > > >
> > > > If QEMU detects xen_ctrl_version = 480, the build will fail against Xen
> > > > 4.9, even when -DXC_WANT_COMPAT_DEVICEMODEL_API=1 is
> > specified.
> > > >
> > > > The appended patch solves the problem. However, Xen 4.9 detection
> > and
> > > > compilation remain broken.
> > >
> > > Ok, that fix looks fine to me.
> > 
> > I merged this change into "use libxendevicemodel when available" in my
> > next branch.
> > 
> > Are you going to take care of getting the QEMU build on ARM to work
> > against Xen 4.9 (properly detecting 4.9, without
> > -DXC_WANT_COMPAT_DEVICEMODEL_API=1)?
> > 
> 
> I can take a look once I get access to some h/w. Since the 4.9 detection 
> should merely be based upon the presence of libxendevicemodel, I can't really 
> imagine why ARM should behave any differently to x86.

I managed to find the time to do some debugging. You are right that is
not anything major. The bug is due to a missing -lxencall in the QEMU
configure script, I wonder why it works on x86.

diff --git a/configure b/configure
index 99d6cbc..363a126 100755
--- a/configure
+++ b/configure
@@ -2027,9 +2027,9 @@ int main(void) {
   return 0;
 }
 EOF
-        compile_prog "" "$xen_libs $xen_stable_libs -lxendevicemodel"
+        compile_prog "" "$xen_libs $xen_stable_libs -lxendevicemodel -lxencall"
       then
-      xen_stable_libs="$xen_stable_libs -lxendevicemodel"
+      xen_stable_libs="$xen_stable_libs -lxendevicemodel -lxencall"
       xen_ctrl_version=40900
       xen=yes
     elif