[v2,1/3] hapvdimm: add a virtual DIMM device for memory hot-add protocols

diff --git a/hw/i386/Kconfig b/hw/i386/Kconfig
index d22ac4a4b9..c248cd3734 100644
--- a/hw/i386/Kconfig
+++ b/hw/i386/Kconfig
@@ -69,6 +69,7 @@  config I440FX
     imply E1000_PCI
     imply VMPORT
     imply VMMOUSE
+    imply HAPVDIMM
     select PC_PCI
     select PC_ACPI
     select ACPI_SMBUS
@@ -96,6 +97,7 @@  config Q35
     imply E1000E_PCI_EXPRESS
     imply VMPORT
     imply VMMOUSE
+    imply HAPVDIMM
     select PC_PCI
     select PC_ACPI
     select PCI_EXPRESS_Q35
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index d489ecc0d1..62b532f9e9 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -73,6 +73,7 @@ 
 #include "hw/acpi/acpi.h"
 #include "hw/acpi/cpu_hotplug.h"
 #include "acpi-build.h"
+#include "hw/mem/hapvdimm.h"
 #include "hw/mem/pc-dimm.h"
 #include "hw/mem/nvdimm.h"
 #include "hw/cxl/cxl.h"
@@ -1610,7 +1611,8 @@  static HotplugHandler *pc_get_hotplug_handler(MachineState *machine,
         object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_PMEM_PCI) ||
         object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_MEM_PCI) ||
         object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_IOMMU_PCI) ||
-        object_dynamic_cast(OBJECT(dev), TYPE_X86_IOMMU_DEVICE)) {
+        object_dynamic_cast(OBJECT(dev), TYPE_X86_IOMMU_DEVICE) ||
+        object_dynamic_cast(OBJECT(dev), TYPE_HAPVDIMM)) {
         return HOTPLUG_HANDLER(machine);
     }
 
diff --git a/hw/mem/Kconfig b/hw/mem/Kconfig
index 73c5ae8ad9..d8c1feafed 100644
--- a/hw/mem/Kconfig
+++ b/hw/mem/Kconfig
@@ -16,3 +16,7 @@  config CXL_MEM_DEVICE
     bool
     default y if CXL
     select MEM_DEVICE
+
+config HAPVDIMM
+    bool
+    select MEM_DEVICE
diff --git a/hw/mem/hapvdimm.c b/hw/mem/hapvdimm.c
new file mode 100644
index 0000000000..9ae82edb2c
--- /dev/null
+++ b/hw/mem/hapvdimm.c
@@ -0,0 +1,221 @@ 
+/*
+ * A memory hot-add protocol vDIMM device
+ *
+ * Copyright (C) 2020-2023 Oracle and/or its affiliates.
+ *
+ * Heavily based on pc-dimm.c:
+ * Copyright ProfitBricks GmbH 2012
+ * Copyright (C) 2014 Red Hat Inc
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+
+#include "exec/memory.h"
+#include "hw/boards.h"
+#include "hw/mem/hapvdimm.h"
+#include "hw/mem/memory-device.h"
+#include "hw/qdev-core.h"
+#include "hw/qdev-properties.h"
+#include "migration/vmstate.h"
+#include "qapi/error.h"
+#include "qapi/visitor.h"
+#include "qemu/module.h"
+#include "sysemu/hostmem.h"
+#include "trace.h"
+
+typedef struct HAPVDIMMDevice {
+    /* private */
+    DeviceState parent_obj;
+
+    /* public */
+    bool ever_realized;
+    uint64_t addr;
+    uint64_t align;
+    uint32_t node;
+    HostMemoryBackend *hostmem;
+} HAPVDIMMDevice;
+
+typedef struct HAPVDIMMDeviceClass {
+    /* private */
+    DeviceClass parent_class;
+} HAPVDIMMDeviceClass;
+
+static bool hapvdimm_adding_allowed;
+static Property hapvdimm_properties[] = {
+    DEFINE_PROP_UINT64(HAPVDIMM_ADDR_PROP, HAPVDIMMDevice, addr, 0),
+    DEFINE_PROP_UINT64(HAPVDIMM_ALIGN_PROP, HAPVDIMMDevice, align, 0),
+    DEFINE_PROP_LINK(HAPVDIMM_MEMDEV_PROP, HAPVDIMMDevice, hostmem,
+                     TYPE_MEMORY_BACKEND, HostMemoryBackend *),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
+void hapvdimm_allow_adding(void)
+{
+    hapvdimm_adding_allowed = true;
+}
+
+void hapvdimm_disallow_adding(void)
+{
+    hapvdimm_adding_allowed = false;
+}
+
+static void hapvdimm_get_size(Object *obj, Visitor *v, const char *name,
+                            void *opaque, Error **errp)
+{
+    ERRP_GUARD();
+    uint64_t value;
+
+    value = memory_device_get_region_size(MEMORY_DEVICE(obj), errp);
+    if (*errp) {
+        return;
+    }
+
+    visit_type_uint64(v, name, &value, errp);
+}
+
+static void hapvdimm_init(Object *obj)
+{
+    object_property_add(obj, HAPVDIMM_SIZE_PROP, "uint64", hapvdimm_get_size,
+                        NULL, NULL, NULL);
+}
+
+static void hapvdimm_realize(DeviceState *dev, Error **errp)
+{
+    ERRP_GUARD();
+    HAPVDIMMDevice *hapvdimm = HAPVDIMM(dev);
+    MachineState *ms = MACHINE(qdev_get_machine());
+
+    if (!hapvdimm->ever_realized) {
+        if (!hapvdimm_adding_allowed) {
+            error_setg(errp, "direct adding not allowed");
+            return;
+        }
+
+        hapvdimm->ever_realized = true;
+    }
+
+    memory_device_pre_plug(MEMORY_DEVICE(hapvdimm), ms,
+                           hapvdimm->align ? &hapvdimm->align : NULL,
+                           errp);
+    if (*errp) {
+        return;
+    }
+
+    if (!hapvdimm->hostmem) {
+        error_setg(errp, "'" HAPVDIMM_MEMDEV_PROP "' property is not set");
+        return;
+    } else if (host_memory_backend_is_mapped(hapvdimm->hostmem)) {
+        const char *path;
+
+        path = object_get_canonical_path_component(OBJECT(hapvdimm->hostmem));
+        error_setg(errp, "can't use already busy memdev: %s", path);
+        return;
+    }
+
+    host_memory_backend_set_mapped(hapvdimm->hostmem, true);
+
+    memory_device_plug(MEMORY_DEVICE(hapvdimm), ms);
+    vmstate_register_ram(host_memory_backend_get_memory(hapvdimm->hostmem),
+                         dev);
+}
+
+static void hapvdimm_unrealize(DeviceState *dev)
+{
+    HAPVDIMMDevice *hapvdimm = HAPVDIMM(dev);
+    MachineState *ms = MACHINE(qdev_get_machine());
+
+    memory_device_unplug(MEMORY_DEVICE(hapvdimm), ms);
+    vmstate_unregister_ram(host_memory_backend_get_memory(hapvdimm->hostmem),
+                           dev);
+
+    host_memory_backend_set_mapped(hapvdimm->hostmem, false);
+}
+
+static uint64_t hapvdimm_md_get_addr(const MemoryDeviceState *md)
+{
+    return object_property_get_uint(OBJECT(md), HAPVDIMM_ADDR_PROP,
+                                    &error_abort);
+}
+
+static void hapvdimm_md_set_addr(MemoryDeviceState *md, uint64_t addr,
+                               Error **errp)
+{
+    object_property_set_uint(OBJECT(md), HAPVDIMM_ADDR_PROP, addr, errp);
+}
+
+static MemoryRegion *hapvdimm_md_get_memory_region(MemoryDeviceState *md,
+                                                 Error **errp)
+{
+    HAPVDIMMDevice *hapvdimm = HAPVDIMM(md);
+
+    if (!hapvdimm->hostmem) {
+        error_setg(errp, "'" HAPVDIMM_MEMDEV_PROP "' property must be set");
+        return NULL;
+    }
+
+    return host_memory_backend_get_memory(hapvdimm->hostmem);
+}
+
+static void hapvdimm_md_fill_device_info(const MemoryDeviceState *md,
+                                       MemoryDeviceInfo *info)
+{
+    PCDIMMDeviceInfo *di = g_new0(PCDIMMDeviceInfo, 1);
+    const DeviceClass *dc = DEVICE_GET_CLASS(md);
+    const HAPVDIMMDevice *hapvdimm = HAPVDIMM(md);
+    const DeviceState *dev = DEVICE(md);
+
+    if (dev->id) {
+        di->id = g_strdup(dev->id);
+    }
+    di->hotplugged = dev->hotplugged;
+    di->hotpluggable = dc->hotpluggable;
+    di->addr = hapvdimm->addr;
+    di->slot = -1;
+    di->node = 0; /* FIXME: report proper node */
+    di->size = object_property_get_uint(OBJECT(hapvdimm), HAPVDIMM_SIZE_PROP,
+                                        NULL);
+    di->memdev = object_get_canonical_path(OBJECT(hapvdimm->hostmem));
+
+    info->u.dimm.data = di;
+    info->type = MEMORY_DEVICE_INFO_KIND_DIMM;
+}
+
+static void hapvdimm_class_init(ObjectClass *oc, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(oc);
+    MemoryDeviceClass *mdc = MEMORY_DEVICE_CLASS(oc);
+
+    dc->realize = hapvdimm_realize;
+    dc->unrealize = hapvdimm_unrealize;
+    device_class_set_props(dc, hapvdimm_properties);
+    dc->desc = "vDIMM for a hot add protocol";
+
+    mdc->get_addr = hapvdimm_md_get_addr;
+    mdc->set_addr = hapvdimm_md_set_addr;
+    mdc->get_plugged_size = memory_device_get_region_size;
+    mdc->get_memory_region = hapvdimm_md_get_memory_region;
+    mdc->fill_device_info = hapvdimm_md_fill_device_info;
+}
+
+static const TypeInfo hapvdimm_info = {
+    .name          = TYPE_HAPVDIMM,
+    .parent        = TYPE_DEVICE,
+    .instance_size = sizeof(HAPVDIMMDevice),
+    .instance_init = hapvdimm_init,
+    .class_init    = hapvdimm_class_init,
+    .class_size    = sizeof(HAPVDIMMDeviceClass),
+    .interfaces = (InterfaceInfo[]) {
+        { TYPE_MEMORY_DEVICE },
+        { }
+    },
+};
+
+static void hapvdimm_register_types(void)
+{
+    type_register_static(&hapvdimm_info);
+}
+
+type_init(hapvdimm_register_types)
diff --git a/hw/mem/meson.build b/hw/mem/meson.build
index 609b2b36fc..5f7a0181d3 100644
--- a/hw/mem/meson.build
+++ b/hw/mem/meson.build
@@ -4,6 +4,7 @@  mem_ss.add(when: 'CONFIG_DIMM', if_true: files('pc-dimm.c'))
 mem_ss.add(when: 'CONFIG_NPCM7XX', if_true: files('npcm7xx_mc.c'))
 mem_ss.add(when: 'CONFIG_NVDIMM', if_true: files('nvdimm.c'))
 mem_ss.add(when: 'CONFIG_CXL_MEM_DEVICE', if_true: files('cxl_type3.c'))
+mem_ss.add(when: 'CONFIG_HAPVDIMM', if_true: files('hapvdimm.c'))
 
 softmmu_ss.add_all(when: 'CONFIG_MEM_DEVICE', if_true: mem_ss)
 
diff --git a/include/hw/mem/hapvdimm.h b/include/hw/mem/hapvdimm.h
new file mode 100644
index 0000000000..bb9a135a52
--- /dev/null
+++ b/include/hw/mem/hapvdimm.h
@@ -0,0 +1,27 @@ 
+/*
+ * A memory hot-add protocol vDIMM device
+ *
+ * Copyright (C) 2020-2023 Oracle and/or its affiliates.
+ *
+ * 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 QEMU_HAPVDIMM_H
+#define QEMU_HAPVDIMM_H
+
+#include "qom/object.h"
+
+#define TYPE_HAPVDIMM "mem-hapvdimm"
+OBJECT_DECLARE_SIMPLE_TYPE(HAPVDIMMDevice, HAPVDIMM)
+
+#define HAPVDIMM_ADDR_PROP "addr"
+#define HAPVDIMM_ALIGN_PROP "align"
+#define HAPVDIMM_SIZE_PROP "size"
+#define HAPVDIMM_MEMDEV_PROP "memdev"
+
+void hapvdimm_allow_adding(void);
+void hapvdimm_disallow_adding(void);
+
+#endif