armvirt: new target

An ARM Cortex-A15 machine provided by QEMU.

Kernel drivers enabled:

 - pl011, uart
 - pl031, rtc
 - pl061, gpio
 - pci-host-generic
 - virtio_{mmio,pci,net,blk,scsi,9p,console,balloon}
 - smp with NR_CPUS=4
 - cpu-hotplug
 - ext4
 - neon, vfp extensions support (otherwise userland will fail with
   illegal instruction signal (code 0x00000004))
 - DEBUG_BUGVERBOSE for debug purposes

Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>

target/linux/armvirt/README

@@ -0,0 +1,34 @@
+This is intended to be used with LEDE project to provide image for use with
+QEMU arm-softmmu virt machine.
+
+Run with qemu-system-arm
+
+	# boot with initramfs embedded in
+	qemu-system-arm -nographic -M virt -m 64 -kernel lede-armvirt-zImage-initramfs
+
+	# boot with accel=kvm
+	qemu-system-arm -nographic -M virt,accel=kvm -cpu host -m 64 -kernel lede-armvirt-zImage-initramfs
+
+	# boot with a separate rootfs
+	qemu-system-arm -nographic -M virt -m 64 -kernel lede-armvirt-zImage \
+	  -drive file=lede-armvirt-root.ext4,format=raw,if=virtio -append 'root=/dev/vda rootwait'
+
+	# boot with local dir as rootfs
+	qemu-system-arm -nographic -M virt -m 64 -kernel lede-armvirt-zImage \
+	  -fsdev local,id=rootdev,path=root-armvirt/,security_model=none \
+	  -device virtio-9p-pci,fsdev=rootdev,mount_tag=/dev/root \
+	  -append 'rootflags=trans=virtio,version=9p2000.L,cache=loose rootfstype=9p'
+
+Run with kvmtool
+
+	# start a named machine
+	lkvm run -k lede-armvirt-zImage -i lede-armvirt-rootfs.cpio --name armvirt0
+
+	# start with virtio-9p rootfs
+	lkvm run -k lede-armvirt-zImage -d root-armvirt/
+
+	# stop "armvirt0"
+	lkvm stop --name armvirt0
+
+	# stop all
+	lkvm stop --all