From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
Date: Wed, 10 Dec 2008 12:50:58 +0000
Subject: kvm-userspace requires kvm capable kernel headers in default search
Message-Id: <493FBB32.8000507@linux.vnet.ibm.com>
MIME-Version: 1
Content-Type: multipart/mixed; boundary="------------000406020101010904030507"
List-Id: <kvm-ppc.vger.kernel.org>
To: kvm <kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, kvm-ppc <kvm-ppc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Hollis Blanchard <hollisb-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>, Avi Kivity <avi-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

This is a multi-part message in MIME format.
--------------000406020101010904030507
Content-Type: text/plain; charset="iso-8859-1"; format="flowed"
Content-Transfer-Encoding: quoted-printable

Hi everyone,
while running a test when updating kvm-userspace for powerpc I found=20
that the current kvm userspace requires kvm kernel headers in the=20
default search path of the used compilers.
I used to update and build in the same kvm-userspace directory for a=20
while and this one had an old stale kernel/include directory which=20
fulfilled all the requirements.
While testing my current patch series on a new git clone of=20
kvm-userspace I wondered why this doesn't work anymore (it worked in my=20
old directory which also had the updated current source).

I switched to x86 to verify that issue there and I found that eventually=20
the issue is in the kvm detection "KVM Probe" part of the qemu=20
configuration in kvm-userspace. It failed not finding kvm headers.
   gcc -m32 -o /tmp/qemu-conf--21885- =20
-I/home/paelzer/Desktop/kvm-userspace/kernel/include=20
/tmp/qemu-conf--21885-.c
   /tmp/qemu-conf--21885-.c:1:23: error: linux/kvm.h: No such file or=20
directory
   /tmp/qemu-conf--21885-.c:3:2: error: #error Invalid KVM version

Looking at the include paths it is worth to note that a current git=20
clone of kvm-userspace has no kernel/include directory anymore. A few=20
questions later to some other kvm developers I found that there headers=20
can be found, but in the default search path of the compiler e.g.=20
/usr/include. In my environment with an older gcc cross compiler for=20
powerpc and no up to date linux headers installed for x86 both=20
architectures failed.

The Solution to that can be done in several ways:
a) we decide that kvm-userspace needs up-to-date kernel headers=20
installed. And modify the KVM Probe at least to tell the user about this=20
possible reason when failing instead of silently switching to "KVM=20
support no".
b) if the user already provide a --kerneldir option to specify where the=20
right includes can be found we should give those configure checks a=20
chance to really reach that. Atm it adds the kernel/include path of the=20
kvm-userspace tree which doesn't exist anymore (except as stale old dir=20
in a lot of source trees out there).
c) I overlooked something and there is an even better or trivial=20
approach :-)

Since this could be solved several very different ways I think its worth=20
a discussion.
As I prefer b) I attached a simple patch example how this could look=20
like :-).

--=20

Gr=FCsse / regards,=20
Christian Ehrhardt
IBM Linux Technology Center, Open Virtualization


--------------000406020101010904030507
Content-Type: text/x-diff;
 name="fix-qemu-kerneldir-include.diff"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline;
 filename="fix-qemu-kerneldir-include.diff"

diff --git a/configure b/configure
index 63f956c..f772bae 100755
--- a/configure
+++ b/configure
@@ -3,6 +3,7 @@
 prefix=/usr/local
 kernelsourcedir=
 kerneldir=/lib/modules/$(uname -r)/build
+qemu_kerneldir=
 cc=gcc
 ld=ld
 objcopy=objcopy
@@ -56,6 +57,7 @@ while [[ "$1" = -* ]]; do
 	    ;;
 	--kerneldir)
 	    kerneldir="$arg"
+	    qemu_kerneldir="$arg"
 	    ;;
 	--with-patched-kernel)
 	    want_module=
@@ -84,9 +86,12 @@ while [[ "$1" = -* ]]; do
     esac
 done
 
-
-#set kenel directory
+#set libkvm kernel directory
 libkvm_kerneldir=$(readlink -f kernel)
+# use libkvm_kerneldir for qemu if no kerneldir option was set
+if test "$qemu_kerneldir" = "" ; then
+    qemu_kerneldir=$libkvm_kerneldir
+fi
 
 case $arch in
     i?86*|x86_64*)
@@ -123,7 +128,7 @@ fi
     --disable-gcc-check \
     --extra-cflags="-I $PWD/../libkvm $qemu_cflags" \
     --extra-ldflags="-L $PWD/../libkvm $qemu_ldflags" \
-    --kerneldir="$libkvm_kerneldir" \
+    --kerneldir="$qemu_kerneldir" \
     --prefix="$prefix" \
     ${cross_prefix:+"--cross-prefix=$cross_prefix"} \
     ${cross_prefix:+"--cpu=$arch"} "${qemu_opts[@]}"

--------------000406020101010904030507--