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>

MAINTAINERS

@@ -2022,6 +2022,11 @@ F: hw/core/generic-loader.c
 F: include/hw/core/generic-loader.h
 F: docs/generic-loader.txt
 
+Guest Loader
+M: Alex Bennée <alex.bennee@linaro.org>
+S: Maintained
+F: hw/core/guest-loader.c
+
 Intel Hexadecimal Object File Loader
 M: Su Hang <suhang16@mails.ucas.ac.cn>
 S: Maintained

hw/core/guest-loader.c

@@ -0,0 +1,145 @@
+/*
+ * 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.
+ */
+
+/*
+ * Much like the generic-loader this is treated as a special device
+ * inside QEMU. However unlike the generic-loader this device is used
+ * to load guest images for hypervisors. As part of that process the
+ * hypervisor needs to have platform information passed to it by the
+ * lower levels of the stack (e.g. firmware/bootloader). If you boot
+ * the hypervisor directly you use the guest-loader to load the Dom0
+ * or equivalent guest images in the right place in the same way a
+ * boot loader would.
+ *
+ * This is only relevant for full system emulation.
+ */
+
+#include "qemu/osdep.h"
+#include "hw/core/cpu.h"
+#include "hw/sysbus.h"
+#include "sysemu/dma.h"
+#include "hw/loader.h"
+#include "hw/qdev-properties.h"
+#include "qapi/error.h"
+#include "qemu/module.h"
+#include "guest-loader.h"
+#include "sysemu/device_tree.h"
+#include "hw/boards.h"
+
+/*
+ * Insert some FDT nodes for the loaded blob.
+ */
+static void loader_insert_platform_data(GuestLoaderState *s, int size,
+                                        Error **errp)
+{
+    MachineState *machine = MACHINE(qdev_get_machine());
+    void *fdt = machine->fdt;
+    g_autofree char *node = g_strdup_printf("/chosen/module@0x%08" PRIx64,
+                                            s->addr);
+    uint64_t reg_attr[2] = {cpu_to_be64(s->addr), cpu_to_be64(size)};
+
+    if (!fdt) {
+        error_setg(errp, "Cannot modify FDT fields if the machine has none");
+        return;
+    }
+
+    qemu_fdt_add_subnode(fdt, node);
+    qemu_fdt_setprop(fdt, node, "reg", &reg_attr, sizeof(reg_attr));
+
+    if (s->kernel) {
+        const char *compat[2] = { "multiboot,module", "multiboot,kernel" };
+        if (qemu_fdt_setprop_string_array(fdt, node, "compatible",
+                                          (char **) &compat,
+                                          ARRAY_SIZE(compat)) < 0) {
+            error_setg(errp, "couldn't set %s/compatible", node);
+            return;
+        }
+        if (s->args) {
+            if (qemu_fdt_setprop_string(fdt, node, "bootargs", s->args) < 0) {
+                error_setg(errp, "couldn't set %s/bootargs", node);
+            }
+        }
+    } else if (s->initrd) {
+        const char *compat[2] = { "multiboot,module", "multiboot,ramdisk" };
+        if (qemu_fdt_setprop_string_array(fdt, node, "compatible",
+                                          (char **) &compat,
+                                          ARRAY_SIZE(compat)) < 0) {
+            error_setg(errp, "couldn't set %s/compatible", node);
+            return;
+        }
+    }
+}
+
+static void guest_loader_realize(DeviceState *dev, Error **errp)
+{
+    GuestLoaderState *s = GUEST_LOADER(dev);
+    char *file = s->kernel ? s->kernel : s->initrd;
+    int size = 0;
+
+    /* Perform some error checking on the user's options */
+    if (s->kernel && s->initrd) {
+        error_setg(errp, "Cannot specify a kernel and initrd in same stanza");
+        return;
+    } else if (!s->kernel && !s->initrd)  {
+        error_setg(errp, "Need to specify a kernel or initrd image");
+        return;
+    } else if (!s->addr) {
+        error_setg(errp, "Need to specify the address of guest blob");
+        return;
+    } else if (s->args && !s->kernel) {
+        error_setg(errp, "Boot args only relevant to kernel blobs");
+    }
+
+    /* Default to the maximum size being the machine's ram size */
+    size = load_image_targphys_as(file, s->addr, current_machine->ram_size,
+                                  NULL);
+    if (size < 0) {
+        error_setg(errp, "Cannot load specified image %s", file);
+        return;
+    }
+
+    /* Now the image is loaded we need to update the platform data */
+    loader_insert_platform_data(s, size, errp);
+}
+
+static Property guest_loader_props[] = {
+    DEFINE_PROP_UINT64("addr", GuestLoaderState, addr, 0),
+    DEFINE_PROP_STRING("kernel", GuestLoaderState, kernel),
+    DEFINE_PROP_STRING("bootargs", GuestLoaderState, args),
+    DEFINE_PROP_STRING("initrd", GuestLoaderState, initrd),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
+static void guest_loader_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+
+    dc->realize = guest_loader_realize;
+    device_class_set_props(dc, guest_loader_props);
+    dc->desc = "Guest Loader";
+    set_bit(DEVICE_CATEGORY_MISC, dc->categories);
+}
+
+static TypeInfo guest_loader_info = {
+    .name = TYPE_GUEST_LOADER,
+    .parent = TYPE_DEVICE,
+    .instance_size = sizeof(GuestLoaderState),
+    .class_init = guest_loader_class_init,
+};
+
+static void guest_loader_register_type(void)
+{
+    type_register_static(&guest_loader_info);
+}
+
+type_init(guest_loader_register_type)

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

hw/core/meson.build

@@ -37,6 +37,8 @@ softmmu_ss.add(files(
   'clock-vmstate.c',
 ))
 
+softmmu_ss.add(when: 'CONFIG_TCG', if_true: files('guest-loader.c'))
+
 specific_ss.add(when: 'CONFIG_SOFTMMU', if_true: files(
   'machine-qmp-cmds.c',
   'numa.c',