if [[ -d qemu-kvm-$1-vpfring-diff ]]
then
	VERSION=$1
else
	VERSION="0.15.1"
	#echo "usage: $0 <supported qemu-kvm version>"
	#exit
fi

if [[ ! -f qemu-kvm-$VERSION.tar.gz ]]
then
	echo ""
	echo "Downloading QEMU/KVM $VERSION from http://downloads.sourceforge.net/project/kvm/qemu-kvm/$VERSION/qemu-kvm-$VERSION.tar.gz"
	echo ""

	wget http://downloads.sourceforge.net/project/kvm/qemu-kvm/$VERSION/qemu-kvm-$VERSION.tar.gz
fi

echo ""
echo "Building QEMU $VERSION working directory"
echo ""

rm -rf qemu-kvm-$VERSION

tar xvzf qemu-kvm-$VERSION.tar.gz

echo ""
echo "Patching QEMU"
echo ""

# Command to generate a patch: diff -u original.c new.c > original.patch
patch qemu-kvm-$VERSION/Makefile.target < qemu-kvm-$VERSION-vpfring-diff/Makefile.target.patch
if [[ -f qemu-kvm-$VERSION-vpfring-diff/virtio-pci.c.patch ]]
then
	patch qemu-kvm-$VERSION/hw/virtio-pci.c < qemu-kvm-$VERSION-vpfring-diff/virtio-pci.c.patch
fi
cp qemu-kvm-$VERSION-vpfring-diff/hw/* qemu-kvm-$VERSION/hw/

echo ""
echo "Configuring QEMU"
echo ""

cd qemu-kvm-$VERSION
./configure --prefix=/usr/local/kvm

cd ..
echo "" 			 		 > Makefile
echo "all:"					>> Makefile
echo "	cd qemu-kvm-$VERSION; make"		>> Makefile
echo "install:"					>> Makefile
echo "	cd qemu-kvm-$VERSION; make install"	>> Makefile
echo "clean:"					>> Makefile
echo "	cd qemu-kvm-$VERSION; make clean"	>> Makefile

echo ""
echo "run 'make && make install'"
echo ""