s390x: virtio-mem support

Let's add our virtio-mem-ccw proxy device and wire it up. We should
be supporting everything (e.g., device unplug, "dynamic-memslots") that
we already support for the virtio-pci variant.

With a Linux guest that supports virtio-mem (and has automatic memory
onlining properly configured) the following example will work:

1. Start a VM with 4G initial memory and a virtio-mem device with a maximum
   capacity of 16GB:

   qemu/build/qemu-system-s390x \
    --enable-kvm \
    -m 4G,maxmem=20G \
    -nographic \
    -smp 8 \
    -hda Fedora-Server-KVM-40-1.14.s390x.qcow2 \
    -chardev socket,id=monitor,path=/var/tmp/monitor,server,nowait \
    -mon chardev=monitor,mode=readline \
    -object memory-backend-ram,id=mem0,size=16G,reserve=off \
    -device virtio-mem-ccw,id=vmem0,memdev=mem0,dynamic-memslots=on

2. Query the current size of virtio-mem device:

    (qemu) info memory-devices
    Memory device [virtio-mem]: "vmem0"
      memaddr: 0x100000000
      node: 0
      requested-size: 0
      size: 0
      max-size: 17179869184
      block-size: 1048576
      memdev: /objects/mem0

3. Request to grow it to 8GB (hotplug 8GB):

    (qemu) qom-set vmem0 requested-size 8G
    (qemu) info memory-devices
    Memory device [virtio-mem]: "vmem0"
      memaddr: 0x100000000
      node: 0
      requested-size: 8589934592
      size: 8589934592
      max-size: 17179869184
      block-size: 1048576
      memdev: /objects/mem0

4. Request to grow to 16GB (hotplug another 8GB):

    (qemu) qom-set vmem0 requested-size 16G
    (qemu) info memory-devices
    Memory device [virtio-mem]: "vmem0"
      memaddr: 0x100000000
      node: 0
      requested-size: 17179869184
      size: 17179869184
      max-size: 17179869184
      block-size: 1048576
      memdev: /objects/mem0

5. Try to hotunplug all memory again, shrinking to 0GB:

    (qemu) qom-set vmem0 requested-size 0G
    (qemu) info memory-devices
    Memory device [virtio-mem]: "vmem0"
      memaddr: 0x100000000
      node: 0
      requested-size: 0
      size: 0
      max-size: 17179869184
      block-size: 1048576
      memdev: /objects/mem0

6. If it worked, unplug the device

    (qemu) device_del vmem0
    (qemu) info memory-devices
    (qemu) object_del mem0

7. Hotplug a new device with a smaller capacity and directly size it to 1GB

    (qemu) object_add memory-backend-ram,id=mem0,size=8G,reserve=off
    (qemu) device_add virtio-mem-ccw,id=vmem0,memdev=mem0,\
                      dynamic-memslots=on,requested-size=1G
    (qemu) info memory-devices
    Memory device [virtio-mem]: "vmem0"
      memaddr: 0x100000000
      node: 0
      requested-size: 1073741824
      size: 1073741824
      max-size: 8589934592
      block-size: 1048576
      memdev: /objects/mem0

Trying to use a virtio-mem device backed by hugetlb into a !hugetlb VM
correctly results in the error:
   ... Memory device uses a bigger page size than initial memory

Note that the virtio-mem driver in Linux will supports 1 MiB (pageblock)
granularity.

Message-ID: <20241219144115.2820241-15-david@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>

MAINTAINERS

@@ -2390,6 +2390,8 @@ W: https://virtio-mem.gitlab.io/
 F: hw/virtio/virtio-mem.c
 F: hw/virtio/virtio-mem-pci.h
 F: hw/virtio/virtio-mem-pci.c
+F: hw/s390x/virtio-ccw-mem.c
+F: hw/s390x/virtio-ccw-mem.h
 F: include/hw/virtio/virtio-mem.h
 
 virtio-snd

hw/s390x/Kconfig

@@ -16,3 +16,4 @@ config S390_CCW_VIRTIO
     select SCLPCONSOLE
     select VIRTIO_CCW
     select MSI_NONBROKEN
+    select VIRTIO_MEM_SUPPORTED

hw/s390x/meson.build

@@ -51,6 +51,7 @@ virtio_ss.add(when: 'CONFIG_VHOST_SCSI', if_true: files('vhost-scsi-ccw.c'))
 virtio_ss.add(when: 'CONFIG_VHOST_VSOCK', if_true: files('vhost-vsock-ccw.c'))
 virtio_ss.add(when: 'CONFIG_VHOST_USER_FS', if_true: files('vhost-user-fs-ccw.c'))
 virtio_ss.add(when: 'CONFIG_VIRTIO_MD', if_true: files('virtio-ccw-md.c'))
+virtio_ss.add(when: 'CONFIG_VIRTIO_MEM', if_true: files('virtio-ccw-mem.c'))
 s390x_ss.add_all(when: 'CONFIG_VIRTIO_CCW', if_true: virtio_ss)
 
 s390x_ss.add(when: 'CONFIG_VIRTIO_MD', if_false: files('virtio-ccw-md-stubs.c'))

hw/s390x/virtio-ccw-mem.c

@@ -0,0 +1,226 @@
+/*
+ * virtio-mem CCW implementation
+ *
+ * Copyright (C) 2024 Red Hat, Inc.
+ *
+ * Authors:
+ *  David Hildenbrand <david@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "hw/qdev-properties.h"
+#include "qapi/error.h"
+#include "qemu/module.h"
+#include "virtio-ccw-mem.h"
+#include "hw/mem/memory-device.h"
+#include "qapi/qapi-events-machine.h"
+#include "qapi/qapi-events-misc.h"
+
+static void virtio_ccw_mem_realize(VirtioCcwDevice *ccw_dev, Error **errp)
+{
+    VirtIOMEMCcw *dev = VIRTIO_MEM_CCW(ccw_dev);
+    DeviceState *vdev = DEVICE(&dev->vdev);
+
+    qdev_realize(vdev, BUS(&ccw_dev->bus), errp);
+}
+
+static void virtio_ccw_mem_set_addr(MemoryDeviceState *md, uint64_t addr,
+                                    Error **errp)
+{
+    object_property_set_uint(OBJECT(md), VIRTIO_MEM_ADDR_PROP, addr, errp);
+}
+
+static uint64_t virtio_ccw_mem_get_addr(const MemoryDeviceState *md)
+{
+    return object_property_get_uint(OBJECT(md), VIRTIO_MEM_ADDR_PROP,
+                                    &error_abort);
+}
+
+static MemoryRegion *virtio_ccw_mem_get_memory_region(MemoryDeviceState *md,
+                                                      Error **errp)
+{
+    VirtIOMEMCcw *dev = VIRTIO_MEM_CCW(md);
+    VirtIOMEM *vmem = &dev->vdev;
+    VirtIOMEMClass *vmc = VIRTIO_MEM_GET_CLASS(vmem);
+
+    return vmc->get_memory_region(vmem, errp);
+}
+
+static void virtio_ccw_mem_decide_memslots(MemoryDeviceState *md,
+                                           unsigned int limit)
+{
+    VirtIOMEMCcw *dev = VIRTIO_MEM_CCW(md);
+    VirtIOMEM *vmem = VIRTIO_MEM(&dev->vdev);
+    VirtIOMEMClass *vmc = VIRTIO_MEM_GET_CLASS(vmem);
+
+    vmc->decide_memslots(vmem, limit);
+}
+
+static unsigned int virtio_ccw_mem_get_memslots(MemoryDeviceState *md)
+{
+    VirtIOMEMCcw *dev = VIRTIO_MEM_CCW(md);
+    VirtIOMEM *vmem = VIRTIO_MEM(&dev->vdev);
+    VirtIOMEMClass *vmc = VIRTIO_MEM_GET_CLASS(vmem);
+
+    return vmc->get_memslots(vmem);
+}
+
+static uint64_t virtio_ccw_mem_get_plugged_size(const MemoryDeviceState *md,
+                                                Error **errp)
+{
+    return object_property_get_uint(OBJECT(md), VIRTIO_MEM_SIZE_PROP,
+                                    errp);
+}
+
+static void virtio_ccw_mem_fill_device_info(const MemoryDeviceState *md,
+                                            MemoryDeviceInfo *info)
+{
+    VirtioMEMDeviceInfo *vi = g_new0(VirtioMEMDeviceInfo, 1);
+    VirtIOMEMCcw *dev = VIRTIO_MEM_CCW(md);
+    VirtIOMEM *vmem = &dev->vdev;
+    VirtIOMEMClass *vpc = VIRTIO_MEM_GET_CLASS(vmem);
+    DeviceState *vdev = DEVICE(md);
+
+    if (vdev->id) {
+        vi->id = g_strdup(vdev->id);
+    }
+
+    /* let the real device handle everything else */
+    vpc->fill_device_info(vmem, vi);
+
+    info->u.virtio_mem.data = vi;
+    info->type = MEMORY_DEVICE_INFO_KIND_VIRTIO_MEM;
+}
+
+static uint64_t virtio_ccw_mem_get_min_alignment(const MemoryDeviceState *md)
+{
+    return object_property_get_uint(OBJECT(md), VIRTIO_MEM_BLOCK_SIZE_PROP,
+                                    &error_abort);
+}
+
+static void virtio_ccw_mem_size_change_notify(Notifier *notifier, void *data)
+{
+    VirtIOMEMCcw *dev = container_of(notifier, VirtIOMEMCcw,
+                                         size_change_notifier);
+    DeviceState *vdev = DEVICE(dev);
+    char *qom_path = object_get_canonical_path(OBJECT(dev));
+    const uint64_t * const size_p = data;
+
+    qapi_event_send_memory_device_size_change(vdev->id, *size_p, qom_path);
+    g_free(qom_path);
+}
+
+static void virtio_ccw_mem_unplug_request_check(VirtIOMDCcw *vmd, Error **errp)
+{
+    VirtIOMEMCcw *dev = VIRTIO_MEM_CCW(vmd);
+    VirtIOMEM *vmem = &dev->vdev;
+    VirtIOMEMClass *vpc = VIRTIO_MEM_GET_CLASS(vmem);
+
+    vpc->unplug_request_check(vmem, errp);
+}
+
+static void virtio_ccw_mem_get_requested_size(Object *obj, Visitor *v,
+                                              const char *name, void *opaque,
+                                              Error **errp)
+{
+    VirtIOMEMCcw *dev = VIRTIO_MEM_CCW(obj);
+
+    object_property_get(OBJECT(&dev->vdev), name, v, errp);
+}
+
+static void virtio_ccw_mem_set_requested_size(Object *obj, Visitor *v,
+                                              const char *name, void *opaque,
+                                              Error **errp)
+{
+    VirtIOMEMCcw *dev = VIRTIO_MEM_CCW(obj);
+    DeviceState *vdev = DEVICE(obj);
+
+    /*
+     * If we passed virtio_ccw_mem_unplug_request_check(), making sure that
+     * the requested size is 0, don't allow modifying the requested size
+     * anymore, otherwise the VM might end up hotplugging memory before
+     * handling the unplug request.
+     */
+    if (vdev->pending_deleted_event) {
+        error_setg(errp, "'%s' cannot be changed if the device is in the"
+                   " process of unplug", name);
+        return;
+    }
+
+    object_property_set(OBJECT(&dev->vdev), name, v, errp);
+}
+
+static Property virtio_ccw_mem_properties[] = {
+    DEFINE_PROP_BIT("ioeventfd", VirtioCcwDevice, flags,
+                    VIRTIO_CCW_FLAG_USE_IOEVENTFD_BIT, true),
+    DEFINE_PROP_UINT32("max_revision", VirtioCcwDevice, max_rev,
+                       VIRTIO_CCW_MAX_REV),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
+static void virtio_ccw_mem_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+    VirtIOCCWDeviceClass *k = VIRTIO_CCW_DEVICE_CLASS(klass);
+    MemoryDeviceClass *mdc = MEMORY_DEVICE_CLASS(klass);
+    VirtIOMDCcwClass *vmdc = VIRTIO_MD_CCW_CLASS(klass);
+
+    k->realize = virtio_ccw_mem_realize;
+    set_bit(DEVICE_CATEGORY_MISC, dc->categories);
+    device_class_set_props(dc, virtio_ccw_mem_properties);
+
+    mdc->get_addr = virtio_ccw_mem_get_addr;
+    mdc->set_addr = virtio_ccw_mem_set_addr;
+    mdc->get_plugged_size = virtio_ccw_mem_get_plugged_size;
+    mdc->get_memory_region = virtio_ccw_mem_get_memory_region;
+    mdc->decide_memslots = virtio_ccw_mem_decide_memslots;
+    mdc->get_memslots = virtio_ccw_mem_get_memslots;
+    mdc->fill_device_info = virtio_ccw_mem_fill_device_info;
+    mdc->get_min_alignment = virtio_ccw_mem_get_min_alignment;
+
+    vmdc->unplug_request_check = virtio_ccw_mem_unplug_request_check;
+}
+
+static void virtio_ccw_mem_instance_init(Object *obj)
+{
+    VirtIOMEMCcw *dev = VIRTIO_MEM_CCW(obj);
+    VirtIOMEMClass *vmc;
+    VirtIOMEM *vmem;
+
+    virtio_instance_init_common(obj, &dev->vdev, sizeof(dev->vdev),
+                                TYPE_VIRTIO_MEM);
+
+    dev->size_change_notifier.notify = virtio_ccw_mem_size_change_notify;
+    vmem = &dev->vdev;
+    vmc = VIRTIO_MEM_GET_CLASS(vmem);
+    /*
+     * We never remove the notifier again, as we expect both devices to
+     * disappear at the same time.
+     */
+    vmc->add_size_change_notifier(vmem, &dev->size_change_notifier);
+
+    object_property_add_alias(obj, VIRTIO_MEM_BLOCK_SIZE_PROP,
+                              OBJECT(&dev->vdev), VIRTIO_MEM_BLOCK_SIZE_PROP);
+    object_property_add_alias(obj, VIRTIO_MEM_SIZE_PROP, OBJECT(&dev->vdev),
+                              VIRTIO_MEM_SIZE_PROP);
+    object_property_add(obj, VIRTIO_MEM_REQUESTED_SIZE_PROP, "size",
+                        virtio_ccw_mem_get_requested_size,
+                        virtio_ccw_mem_set_requested_size, NULL, NULL);
+}
+
+static const TypeInfo virtio_ccw_mem = {
+    .name = TYPE_VIRTIO_MEM_CCW,
+    .parent = TYPE_VIRTIO_MD_CCW,
+    .instance_size = sizeof(VirtIOMEMCcw),
+    .instance_init = virtio_ccw_mem_instance_init,
+    .class_init = virtio_ccw_mem_class_init,
+};
+
+static void virtio_ccw_mem_register_types(void)
+{
+    type_register_static(&virtio_ccw_mem);
+}
+type_init(virtio_ccw_mem_register_types)

hw/s390x/virtio-ccw-mem.h

@@ -0,0 +1,34 @@
+/*
+ * Virtio MEM CCW device
+ *
+ * Copyright (C) 2024 Red Hat, Inc.
+ *
+ * Authors:
+ *  David Hildenbrand <david@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef HW_S390X_VIRTIO_CCW_MEM_H
+#define HW_S390X_VIRTIO_CCW_MEM_H
+
+#include "virtio-ccw-md.h"
+#include "hw/virtio/virtio-mem.h"
+#include "qom/object.h"
+
+typedef struct VirtIOMEMCcw VirtIOMEMCcw;
+
+/*
+ * virtio-mem-ccw: This extends VirtIOMDCcw
+ */
+#define TYPE_VIRTIO_MEM_CCW "virtio-mem-ccw"
+DECLARE_INSTANCE_CHECKER(VirtIOMEMCcw, VIRTIO_MEM_CCW, TYPE_VIRTIO_MEM_CCW)
+
+struct VirtIOMEMCcw {
+    VirtIOMDCcw parent_obj;
+    VirtIOMEM vdev;
+    Notifier size_change_notifier;
+};
+
+#endif /* HW_S390X_VIRTIO_CCW_MEM_H */

hw/virtio/virtio-mem.c

@@ -61,6 +61,8 @@ static uint32_t virtio_mem_default_thp_size(void)
     } else if (qemu_real_host_page_size() == 64 * KiB) {
         default_thp_size = 512 * MiB;
     }
+#elif defined(__s390x__)
+    default_thp_size = 1 * MiB;
 #endif
 
     return default_thp_size;
@@ -168,7 +170,7 @@ static bool virtio_mem_has_shared_zeropage(RAMBlock *rb)
  * necessary (as the section size can change). But it's more likely that the
  * section size will rather get smaller and not bigger over time.
  */
-#if defined(TARGET_X86_64) || defined(TARGET_I386)
+#if defined(TARGET_X86_64) || defined(TARGET_I386) || defined(TARGET_S390X)
 #define VIRTIO_MEM_USABLE_EXTENT (2 * (128 * MiB))
 #elif defined(TARGET_ARM)
 #define VIRTIO_MEM_USABLE_EXTENT (2 * (512 * MiB))