vdpa: introduce virtio pci driver

This patch introduce a vDPA driver for virtio-pci device. It bridges
the virtio-pci control command to the vDPA bus. This will be used for
features prototyping and testing.

Note that get/restore virtqueue state is not supported which needs
extension on the virtio specification.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20210223061905.422659-4-jasowang@redhat.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/Makefile

@@ -42,6 +42,7 @@ obj-$(CONFIG_DMADEVICES)	+= dma/
 obj-y				+= soc/
 
 obj-$(CONFIG_VIRTIO)		+= virtio/
+obj-$(CONFIG_VIRTIO_PCI_LIB)	+= virtio/
 obj-$(CONFIG_VDPA)		+= vdpa/
 obj-$(CONFIG_XEN)		+= xen/
 

drivers/vdpa/Kconfig

@@ -52,4 +52,11 @@ config MLX5_VDPA_NET
 	  be executed by the hardware. It also supports a variety of stateless
 	  offloads depending on the actual device used and firmware version.
 
+config VP_VDPA
+	tristate "Virtio PCI bridge vDPA driver"
+	select VIRTIO_PCI_LIB
+	depends on PCI_MSI
+	help
+	  This kernel module bridges virtio PCI device to vDPA bus.
+
 endif # VDPA

drivers/vdpa/Makefile

@@ -3,3 +3,4 @@ obj-$(CONFIG_VDPA) += vdpa.o
 obj-$(CONFIG_VDPA_SIM) += vdpa_sim/
 obj-$(CONFIG_IFCVF)    += ifcvf/
 obj-$(CONFIG_MLX5_VDPA) += mlx5/
+obj-$(CONFIG_VP_VDPA)    += virtio_pci/

drivers/vdpa/virtio_pci/Makefile

@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_VP_VDPA) += vp_vdpa.o