hw/core: implement a guest-loader to support static hypervisor guests

Hypervisors, especially type-1 ones, need the firmware/bootcode to put
their initial guest somewhere in memory and pass the information to it
via platform data. The guest-loader is modelled after the generic
loader for exactly this sort of purpose:

  $QEMU $ARGS  -kernel ~/xen.git/xen/xen \
    -append "dom0_mem=1G,max:1G loglvl=all guest_loglvl=all" \
    -device guest-loader,addr=0x42000000,kernel=Image,bootargs="root=/dev/sda2 ro console=hvc0 earlyprintk=xen" \
    -device guest-loader,addr=0x47000000,initrd=rootfs.cpio

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20210303173642.3805-5-alex.bennee@linaro.org>

hw/core/guest-loader.h

@@ -0,0 +1,34 @@
+/*
+ * Guest Loader
+ *
+ * Copyright (C) 2020 Linaro
+ * Written by Alex Bennée <alex.bennee@linaro.org>
+ * (based on the generic-loader by Li Guang <lig.fnst@cn.fujitsu.com>)
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef GUEST_LOADER_H
+#define GUEST_LOADER_H
+
+#include "hw/qdev-core.h"
+#include "qom/object.h"
+
+struct GuestLoaderState {
+    /* <private> */
+    DeviceState parent_obj;
+
+    /* <public> */
+    uint64_t addr;
+    char *kernel;
+    char *args;
+    char *initrd;
+};
+
+#define TYPE_GUEST_LOADER "guest-loader"
+OBJECT_DECLARE_SIMPLE_TYPE(GuestLoaderState, GUEST_LOADER)
+
+#endif