Introduce Virtio-loopback epsilon release:

Epsilon release introduces a new compatibility layer which make virtio-loopback
design to work with QEMU and rust-vmm vhost-user backend without require any
changes.

Signed-off-by: Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
Change-Id: I52e57563e08a7d0bdc002f8e928ee61ba0c53dd9

1 files changed, 109 insertions, 0 deletions

diff --git a/hw/misc/empty_slot.c b/hw/misc/empty_slot.c
new file mode 100644
index 000000000..37b0ddfb0
--- /dev/null
+++ b/hw/misc/empty_slot.c
@@ -0,0 +1,109 @@
+/*
+ * QEMU Empty Slot
+ *
+ * The empty_slot device emulates known to a bus but not connected devices.
+ *
+ * Copyright (c) 2010 Artyom Tarasenko
+ *
+ * This code is licensed under the GNU GPL v2 or (at your option) any later
+ * version.
+ */
+
+#include "qemu/osdep.h"
+#include "hw/sysbus.h"
+#include "hw/qdev-properties.h"
+#include "hw/misc/empty_slot.h"
+#include "qapi/error.h"
+#include "trace.h"
+#include "qom/object.h"
+
+#define TYPE_EMPTY_SLOT "empty_slot"
+OBJECT_DECLARE_SIMPLE_TYPE(EmptySlot, EMPTY_SLOT)
+
+struct EmptySlot {
+    SysBusDevice parent_obj;
+
+    MemoryRegion iomem;
+    char *name;
+    uint64_t size;
+};
+
+static uint64_t empty_slot_read(void *opaque, hwaddr addr,
+                                unsigned size)
+{
+    EmptySlot *s = EMPTY_SLOT(opaque);
+
+    trace_empty_slot_write(addr, size << 1, 0, size, s->name);
+
+    return 0;
+}
+
+static void empty_slot_write(void *opaque, hwaddr addr,
+                             uint64_t val, unsigned size)
+{
+    EmptySlot *s = EMPTY_SLOT(opaque);
+
+    trace_empty_slot_write(addr, size << 1, val, size, s->name);
+}
+
+static const MemoryRegionOps empty_slot_ops = {
+    .read = empty_slot_read,
+    .write = empty_slot_write,
+    .endianness = DEVICE_NATIVE_ENDIAN,
+};
+
+void empty_slot_init(const char *name, hwaddr addr, uint64_t slot_size)
+{
+    if (slot_size > 0) {
+        /* Only empty slots larger than 0 byte need handling. */
+        DeviceState *dev;
+
+        dev = qdev_new(TYPE_EMPTY_SLOT);
+
+        qdev_prop_set_uint64(dev, "size", slot_size);
+        sysbus_realize_and_unref(SYS_BUS_DEVICE(dev), &error_fatal);
+
+        sysbus_mmio_map_overlap(SYS_BUS_DEVICE(dev), 0, addr, -10000);
+    }
+}
+
+static void empty_slot_realize(DeviceState *dev, Error **errp)
+{
+    EmptySlot *s = EMPTY_SLOT(dev);
+
+    if (s->name == NULL) {
+        s->name = g_strdup("empty-slot");
+    }
+    memory_region_init_io(&s->iomem, OBJECT(s), &empty_slot_ops, s,
+                          s->name, s->size);
+    sysbus_init_mmio(SYS_BUS_DEVICE(dev), &s->iomem);
+}
+
+static Property empty_slot_properties[] = {
+    DEFINE_PROP_UINT64("size", EmptySlot, size, 0),
+    DEFINE_PROP_STRING("name", EmptySlot, name),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
+static void empty_slot_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+
+    dc->realize = empty_slot_realize;
+    device_class_set_props(dc, empty_slot_properties);
+    set_bit(DEVICE_CATEGORY_MISC, dc->categories);
+}
+
+static const TypeInfo empty_slot_info = {
+    .name          = TYPE_EMPTY_SLOT,
+    .parent        = TYPE_SYS_BUS_DEVICE,
+    .instance_size = sizeof(EmptySlot),
+    .class_init    = empty_slot_class_init,
+};
+
+static void empty_slot_register_types(void)
+{
+    type_register_static(&empty_slot_info);
+}
+
+type_init(empty_slot_register_types)