kvm: external module: Make KVM compile on split source/object kernel configurations

KVM as is assumes that the kernel obj dir and the kernel source dir are
at the same location. This is true for most self-built vanilla kernels,
but some distributions split these up (e.g. SUSE).
To keep compatible and have users have a good experience on building KVM
on any distribution, this patch attempts to rebuild the logic from the
kernel Makefile as closely as possible. With it I successfully built KVM
on a current SUSE system.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/configure b/configure
index f6727bf0..3b5d14fa 100755
--- a/configure
+++ b/configure
@@ -1,6 +1,7 @@
 #!/bin/bash
 
 prefix=/usr/local
+kernelsourcedir=
 kerneldir=/lib/modules/$(uname -r)/build
 cc=gcc
 ld=ld
@@ -107,6 +108,11 @@ if [ "$arch" = "powerpc" ]; then
     qemu_ldflags="$qemu_ldflags -L $PWD/libfdt"
 fi
 
+# see if we have split build and source directories
+if [ -d "$kerneldir/include2" ]; then
+    kernelsourcedir=${kerneldir%/*}/source
+fi
+
 #configure user dir
 (cd user; ./configure --prefix="$prefix" --kerneldir="$libkvm_kerneldir" \
           --arch="$arch" \
@@ -129,6 +135,7 @@ cat <<EOF > config.mak
 ARCH=$arch
 PREFIX=$prefix
 KERNELDIR=$kerneldir
+KERNELSOURCEDIR=$kernelsourcedir
 LIBKVM_KERNELDIR=$libkvm_kerneldir
 WANT_MODULE=$want_module
 CROSS_COMPILE=$cross_prefix