Re: [Qemu-devel] [PATCH] MAkefile: dont rebuild vhost for each target

[Stefan Hajnoczi]

On Thu, Dec 20, 2012 at 04:20:37PM +0200, Michael S. Tsirkin wrote:
> diff --git a/hw/Makefile.objs b/hw/Makefile.objs
> index 2778035..360a43c 100644
> --- a/hw/Makefile.objs
> +++ b/hw/Makefile.objs
> @@ -3,6 +3,9 @@ common-obj-y += loader.o
>  common-obj-$(CONFIG_VIRTIO) += virtio-console.o
>  common-obj-$(CONFIG_VIRTIO) += virtio-rng.o
>  common-obj-$(CONFIG_VIRTIO_PCI) += virtio-pci.o
> +common-obj-$(CONFIG_VHOST_NET) += vhost_net.o
> +common-obj-$(CONFIG_VHOST_NET) += vhost.o
> +common-obj-$(CONFIG_NO_VHOST_NET) += vhost_net_stub.o
>  common-obj-y += fw_cfg.o
>  common-obj-$(CONFIG_PCI) += pci_bridge_dev.o
>  common-obj-$(CONFIG_PCI) += ioh3420.o xio3130_upstream.o xio3130_downstream.o
> @@ -192,8 +195,6 @@ common-obj-$(CONFIG_XEN_BACKEND) += xen_console.o xenfb.o 
> xen_disk.o xen_nic.o
>  # need to fix this properly
>  obj-$(CONFIG_VIRTIO) += virtio.o virtio-blk.o virtio-balloon.o virtio-net.o
>  obj-$(CONFIG_VIRTIO) += virtio-serial-bus.o virtio-scsi.o
> -obj-$(CONFIG_SOFTMMU) += vhost_net.o
> -obj-$(CONFIG_VHOST_NET) += vhost.o
>  obj-$(CONFIG_REALLY_VIRTFS) += 9pfs/
>  obj-$(CONFIG_VGA) += vga.o
>  obj-$(CONFIG_SOFTMMU) += device-hotplug.o

Careful, this change means that you're now including the system-wide
/usr/include/linux/vhost.h header file instead of QEMU's
linux-headers/linux/vhost.h.

I recently hit this with the dataplane patches since they include
virtio_ring.h.

On an outdated build host we may run into trouble when relying on the
system-wide header file.

(The -I linux-headers/ is only added in Makefile.target.)

Stefan