x86, platform, kvm, kconfig: Turn existing .config's into KVM-capable configs

Add an config file snippet which enables additional options
useful for running the kernel in a kvm guest. When you execute
'make kvmconfig' it merges those options with an already
existing user config before you build the kernel.

Based on an patch from the external lkvm tree.

Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: penberg@kernel.org
Cc: levinsasha928@gmail.com
Cc: mtosatti@redhat.com
Cc: fengguang.wu@intel.com
Link: http://lkml.kernel.org/r/20130522144638.GB15085@pd.tnic
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/Makefile

@@ -220,6 +220,11 @@ archclean:
 	$(Q)$(MAKE) $(clean)=$(boot)
 	$(Q)$(MAKE) $(clean)=arch/x86/tools
 
+kvmconfig:
+	$(if $(wildcard $(objtree)/.config),, $(error You need an existing .config for this target))
+	$(Q)$(CONFIG_SHELL) $(srctree)/scripts/kconfig/merge_config.sh -m -O $(objtree) $(objtree)/.config arch/x86/configs/kvm_guest.config
+	$(Q)yes "" | $(MAKE) oldconfig
+
 define archhelp
   echo  '* bzImage      - Compressed kernel image (arch/x86/boot/bzImage)'
   echo  '  install      - Install kernel using'
@@ -233,4 +238,5 @@ define archhelp
   echo  '                  bzdisk/fdimage*/isoimage also accept:'
   echo  '                  FDARGS="..."  arguments for the booted kernel'
   echo  '                  FDINITRD=file initrd for the booted kernel'
+  echo  '  kvmconfig	- Enable additional options for guest kernel support'
 endef

arch/x86/configs/kvm_guest.config

@@ -0,0 +1,28 @@
+CONFIG_NET=y
+CONFIG_NET_CORE=y
+CONFIG_NETDEVICES=y
+CONFIG_BLOCK=y
+CONFIG_BLK_DEV=y
+CONFIG_NETWORK_FILESYSTEMS=y
+CONFIG_INET=y
+CONFIG_TTY=y
+CONFIG_SERIAL_8250=y
+CONFIG_SERIAL_8250_CONSOLE=y
+CONFIG_IP_PNP=y
+CONFIG_IP_PNP_DHCP=y
+CONFIG_BINFMT_ELF=y
+CONFIG_PCI=y
+CONFIG_PCI_MSI=y
+CONFIG_DEBUG_KERNEL=y
+CONFIG_VIRTUALIZATION=y
+CONFIG_HYPERVISOR_GUEST=y
+CONFIG_PARAVIRT=y
+CONFIG_KVM_GUEST=y
+CONFIG_VIRTIO=y
+CONFIG_VIRTIO_PCI=y
+CONFIG_VIRTIO_BLK=y
+CONFIG_VIRTIO_CONSOLE=y
+CONFIG_VIRTIO_NET=y
+CONFIG_9P_FS=y
+CONFIG_NET_9P=y
+CONFIG_NET_9P_VIRTIO=y