qemu

virtio-mem.c (46431B)

---

 /*
  * Virtio MEM device
  *
  * Copyright (C) 2020 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 "qemu/iov.h"
 #include "qemu/cutils.h"
 #include "qemu/error-report.h"
 #include "qemu/units.h"
 #include "sysemu/numa.h"
 #include "sysemu/sysemu.h"
 #include "sysemu/reset.h"
 #include "hw/virtio/virtio.h"
 #include "hw/virtio/virtio-bus.h"
 #include "hw/virtio/virtio-access.h"
 #include "hw/virtio/virtio-mem.h"
 #include "qapi/error.h"
 #include "qapi/visitor.h"
 #include "exec/ram_addr.h"
 #include "migration/misc.h"
 #include "hw/boards.h"
 #include "hw/qdev-properties.h"
 #include CONFIG_DEVICES
 #include "trace.h"
 
 /*
  * We only had legacy x86 guests that did not support
  * VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE. Other targets don't have legacy guests.
  */
 #if defined(TARGET_X86_64) || defined(TARGET_I386)
 #define VIRTIO_MEM_HAS_LEGACY_GUESTS
 #endif
 
 /*
  * Let's not allow blocks smaller than 1 MiB, for example, to keep the tracking
  * bitmap small.
  */
 #define VIRTIO_MEM_MIN_BLOCK_SIZE ((uint32_t)(1 * MiB))
 
 static uint32_t virtio_mem_default_thp_size(void)
 {
     uint32_t default_thp_size = VIRTIO_MEM_MIN_BLOCK_SIZE;
 
 #if defined(__x86_64__) || defined(__arm__) || defined(__powerpc64__)
     default_thp_size = 2 * MiB;
 #elif defined(__aarch64__)
     if (qemu_real_host_page_size() == 4 * KiB) {
         default_thp_size = 2 * MiB;
     } else if (qemu_real_host_page_size() == 16 * KiB) {
         default_thp_size = 32 * MiB;
     } else if (qemu_real_host_page_size() == 64 * KiB) {
         default_thp_size = 512 * MiB;
     }
 #endif
 
     return default_thp_size;
 }
 
 /*
  * We want to have a reasonable default block size such that
  * 1. We avoid splitting THPs when unplugging memory, which degrades
  *    performance.
  * 2. We avoid placing THPs for plugged blocks that also cover unplugged
  *    blocks.
  *
  * The actual THP size might differ between Linux kernels, so we try to probe
  * it. In the future (if we ever run into issues regarding 2.), we might want
  * to disable THP in case we fail to properly probe the THP size, or if the
  * block size is configured smaller than the THP size.
  */
 static uint32_t thp_size;
 
 #define HPAGE_PMD_SIZE_PATH "/sys/kernel/mm/transparent_hugepage/hpage_pmd_size"
 static uint32_t virtio_mem_thp_size(void)
 {
     gchar *content = NULL;
     const char *endptr;
     uint64_t tmp;
 
     if (thp_size) {
         return thp_size;
     }
 
     /*
      * Try to probe the actual THP size, fallback to (sane but eventually
      * incorrect) default sizes.
      */
     if (g_file_get_contents(HPAGE_PMD_SIZE_PATH, &content, NULL, NULL) &&
         !qemu_strtou64(content, &endptr, 0, &tmp) &&
         (!endptr || *endptr == '\n')) {
         /* Sanity-check the value and fallback to something reasonable. */
         if (!tmp || !is_power_of_2(tmp)) {
             warn_report("Read unsupported THP size: %" PRIx64, tmp);
         } else {
             thp_size = tmp;
         }
     }
 
     if (!thp_size) {
         thp_size = virtio_mem_default_thp_size();
         warn_report("Could not detect THP size, falling back to %" PRIx64
                     "  MiB.", thp_size / MiB);
     }
 
     g_free(content);
     return thp_size;
 }
 
 static uint64_t virtio_mem_default_block_size(RAMBlock *rb)
 {
     const uint64_t page_size = qemu_ram_pagesize(rb);
 
     /* We can have hugetlbfs with a page size smaller than the THP size. */
     if (page_size == qemu_real_host_page_size()) {
         return MAX(page_size, virtio_mem_thp_size());
     }
     return MAX(page_size, VIRTIO_MEM_MIN_BLOCK_SIZE);
 }
 
 #if defined(VIRTIO_MEM_HAS_LEGACY_GUESTS)
 static bool virtio_mem_has_shared_zeropage(RAMBlock *rb)
 {
     /*
      * We only have a guaranteed shared zeropage on ordinary MAP_PRIVATE
      * anonymous RAM. In any other case, reading unplugged *can* populate a
      * fresh page, consuming actual memory.
      */
     return !qemu_ram_is_shared(rb) && rb->fd < 0 &&
            qemu_ram_pagesize(rb) == qemu_real_host_page_size();
 }
 #endif /* VIRTIO_MEM_HAS_LEGACY_GUESTS */
 
 /*
  * Size the usable region bigger than the requested size if possible. Esp.
  * Linux guests will only add (aligned) memory blocks in case they fully
  * fit into the usable region, but plug+online only a subset of the pages.
  * The memory block size corresponds mostly to the section size.
  *
  * This allows e.g., to add 20MB with a section size of 128MB on x86_64, and
  * a section size of 512MB on arm64 (as long as the start address is properly
  * aligned, similar to ordinary DIMMs).
  *
  * We can change this at any time and maybe even make it configurable if
  * 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)
 #define VIRTIO_MEM_USABLE_EXTENT (2 * (128 * MiB))
 #elif defined(TARGET_ARM)
 #define VIRTIO_MEM_USABLE_EXTENT (2 * (512 * MiB))
 #else
 #error VIRTIO_MEM_USABLE_EXTENT not defined
 #endif
 
 static bool virtio_mem_is_busy(void)
 {
     /*
      * Postcopy cannot handle concurrent discards and we don't want to migrate
      * pages on-demand with stale content when plugging new blocks.
      *
      * For precopy, we don't want unplugged blocks in our migration stream, and
      * when plugging new blocks, the page content might differ between source
      * and destination (observable by the guest when not initializing pages
      * after plugging them) until we're running on the destination (as we didn't
      * migrate these blocks when they were unplugged).
      */
     return migration_in_incoming_postcopy() || !migration_is_idle();
 }
 
 typedef int (*virtio_mem_range_cb)(const VirtIOMEM *vmem, void *arg,
                                    uint64_t offset, uint64_t size);
 
 static int virtio_mem_for_each_unplugged_range(const VirtIOMEM *vmem, void *arg,
                                                virtio_mem_range_cb cb)
 {
     unsigned long first_zero_bit, last_zero_bit;
     uint64_t offset, size;
     int ret = 0;
 
     first_zero_bit = find_first_zero_bit(vmem->bitmap, vmem->bitmap_size);
     while (first_zero_bit < vmem->bitmap_size) {
         offset = first_zero_bit * vmem->block_size;
         last_zero_bit = find_next_bit(vmem->bitmap, vmem->bitmap_size,
                                       first_zero_bit + 1) - 1;
         size = (last_zero_bit - first_zero_bit + 1) * vmem->block_size;
 
         ret = cb(vmem, arg, offset, size);
         if (ret) {
             break;
         }
         first_zero_bit = find_next_zero_bit(vmem->bitmap, vmem->bitmap_size,
                                             last_zero_bit + 2);
     }
     return ret;
 }
 
 /*
  * Adjust the memory section to cover the intersection with the given range.
  *
  * Returns false if the intersection is empty, otherwise returns true.
  */
 static bool virito_mem_intersect_memory_section(MemoryRegionSection *s,
                                                 uint64_t offset, uint64_t size)
 {
     uint64_t start = MAX(s->offset_within_region, offset);
     uint64_t end = MIN(s->offset_within_region + int128_get64(s->size),
                        offset + size);
 
     if (end <= start) {
         return false;
     }
 
     s->offset_within_address_space += start - s->offset_within_region;
     s->offset_within_region = start;
     s->size = int128_make64(end - start);
     return true;
 }
 
 typedef int (*virtio_mem_section_cb)(MemoryRegionSection *s, void *arg);
 
 static int virtio_mem_for_each_plugged_section(const VirtIOMEM *vmem,
                                                MemoryRegionSection *s,
                                                void *arg,
                                                virtio_mem_section_cb cb)
 {
     unsigned long first_bit, last_bit;
     uint64_t offset, size;
     int ret = 0;
 
     first_bit = s->offset_within_region / vmem->bitmap_size;
     first_bit = find_next_bit(vmem->bitmap, vmem->bitmap_size, first_bit);
     while (first_bit < vmem->bitmap_size) {
         MemoryRegionSection tmp = *s;
 
         offset = first_bit * vmem->block_size;
         last_bit = find_next_zero_bit(vmem->bitmap, vmem->bitmap_size,
                                       first_bit + 1) - 1;
         size = (last_bit - first_bit + 1) * vmem->block_size;
 
         if (!virito_mem_intersect_memory_section(&tmp, offset, size)) {
             break;
         }
         ret = cb(&tmp, arg);
         if (ret) {
             break;
         }
         first_bit = find_next_bit(vmem->bitmap, vmem->bitmap_size,
                                   last_bit + 2);
     }
     return ret;
 }
 
 static int virtio_mem_for_each_unplugged_section(const VirtIOMEM *vmem,
                                                  MemoryRegionSection *s,
                                                  void *arg,
                                                  virtio_mem_section_cb cb)
 {
     unsigned long first_bit, last_bit;
     uint64_t offset, size;
     int ret = 0;
 
     first_bit = s->offset_within_region / vmem->bitmap_size;
     first_bit = find_next_zero_bit(vmem->bitmap, vmem->bitmap_size, first_bit);
     while (first_bit < vmem->bitmap_size) {
         MemoryRegionSection tmp = *s;
 
         offset = first_bit * vmem->block_size;
         last_bit = find_next_bit(vmem->bitmap, vmem->bitmap_size,
                                  first_bit + 1) - 1;
         size = (last_bit - first_bit + 1) * vmem->block_size;
 
         if (!virito_mem_intersect_memory_section(&tmp, offset, size)) {
             break;
         }
         ret = cb(&tmp, arg);
         if (ret) {
             break;
         }
         first_bit = find_next_zero_bit(vmem->bitmap, vmem->bitmap_size,
                                        last_bit + 2);
     }
     return ret;
 }
 
 static int virtio_mem_notify_populate_cb(MemoryRegionSection *s, void *arg)
 {
     RamDiscardListener *rdl = arg;
 
     return rdl->notify_populate(rdl, s);
 }
 
 static int virtio_mem_notify_discard_cb(MemoryRegionSection *s, void *arg)
 {
     RamDiscardListener *rdl = arg;
 
     rdl->notify_discard(rdl, s);
     return 0;
 }
 
 static void virtio_mem_notify_unplug(VirtIOMEM *vmem, uint64_t offset,
                                      uint64_t size)
 {
     RamDiscardListener *rdl;
 
     QLIST_FOREACH(rdl, &vmem->rdl_list, next) {
         MemoryRegionSection tmp = *rdl->section;
 
         if (!virito_mem_intersect_memory_section(&tmp, offset, size)) {
             continue;
         }
         rdl->notify_discard(rdl, &tmp);
     }
 }
 
 static int virtio_mem_notify_plug(VirtIOMEM *vmem, uint64_t offset,
                                   uint64_t size)
 {
     RamDiscardListener *rdl, *rdl2;
     int ret = 0;
 
     QLIST_FOREACH(rdl, &vmem->rdl_list, next) {
         MemoryRegionSection tmp = *rdl->section;
 
         if (!virito_mem_intersect_memory_section(&tmp, offset, size)) {
             continue;
         }
         ret = rdl->notify_populate(rdl, &tmp);
         if (ret) {
             break;
         }
     }
 
     if (ret) {
         /* Notify all already-notified listeners. */
         QLIST_FOREACH(rdl2, &vmem->rdl_list, next) {
             MemoryRegionSection tmp = *rdl->section;
 
             if (rdl2 == rdl) {
                 break;
             }
             if (!virito_mem_intersect_memory_section(&tmp, offset, size)) {
                 continue;
             }
             rdl2->notify_discard(rdl2, &tmp);
         }
     }
     return ret;
 }
 
 static void virtio_mem_notify_unplug_all(VirtIOMEM *vmem)
 {
     RamDiscardListener *rdl;
 
     if (!vmem->size) {
         return;
     }
 
     QLIST_FOREACH(rdl, &vmem->rdl_list, next) {
         if (rdl->double_discard_supported) {
             rdl->notify_discard(rdl, rdl->section);
         } else {
             virtio_mem_for_each_plugged_section(vmem, rdl->section, rdl,
                                                 virtio_mem_notify_discard_cb);
         }
     }
 }
 
 static bool virtio_mem_test_bitmap(const VirtIOMEM *vmem, uint64_t start_gpa,
                                    uint64_t size, bool plugged)
 {
     const unsigned long first_bit = (start_gpa - vmem->addr) / vmem->block_size;
     const unsigned long last_bit = first_bit + (size / vmem->block_size) - 1;
     unsigned long found_bit;
 
     /* We fake a shorter bitmap to avoid searching too far. */
     if (plugged) {
         found_bit = find_next_zero_bit(vmem->bitmap, last_bit + 1, first_bit);
     } else {
         found_bit = find_next_bit(vmem->bitmap, last_bit + 1, first_bit);
     }
     return found_bit > last_bit;
 }
 
 static void virtio_mem_set_bitmap(VirtIOMEM *vmem, uint64_t start_gpa,
                                   uint64_t size, bool plugged)
 {
     const unsigned long bit = (start_gpa - vmem->addr) / vmem->block_size;
     const unsigned long nbits = size / vmem->block_size;
 
     if (plugged) {
         bitmap_set(vmem->bitmap, bit, nbits);
     } else {
         bitmap_clear(vmem->bitmap, bit, nbits);
     }
 }
 
 static void virtio_mem_send_response(VirtIOMEM *vmem, VirtQueueElement *elem,
                                      struct virtio_mem_resp *resp)
 {
     VirtIODevice *vdev = VIRTIO_DEVICE(vmem);
     VirtQueue *vq = vmem->vq;
 
     trace_virtio_mem_send_response(le16_to_cpu(resp->type));
     iov_from_buf(elem->in_sg, elem->in_num, 0, resp, sizeof(*resp));
 
     virtqueue_push(vq, elem, sizeof(*resp));
     virtio_notify(vdev, vq);
 }
 
 static void virtio_mem_send_response_simple(VirtIOMEM *vmem,
                                             VirtQueueElement *elem,
                                             uint16_t type)
 {
     struct virtio_mem_resp resp = {
         .type = cpu_to_le16(type),
     };
 
     virtio_mem_send_response(vmem, elem, &resp);
 }
 
 static bool virtio_mem_valid_range(const VirtIOMEM *vmem, uint64_t gpa,
                                    uint64_t size)
 {
     if (!QEMU_IS_ALIGNED(gpa, vmem->block_size)) {
         return false;
     }
     if (gpa + size < gpa || !size) {
         return false;
     }
     if (gpa < vmem->addr || gpa >= vmem->addr + vmem->usable_region_size) {
         return false;
     }
     if (gpa + size > vmem->addr + vmem->usable_region_size) {
         return false;
     }
     return true;
 }
 
 static int virtio_mem_set_block_state(VirtIOMEM *vmem, uint64_t start_gpa,
                                       uint64_t size, bool plug)
 {
     const uint64_t offset = start_gpa - vmem->addr;
     RAMBlock *rb = vmem->memdev->mr.ram_block;
 
     if (virtio_mem_is_busy()) {
         return -EBUSY;
     }
 
     if (!plug) {
         if (ram_block_discard_range(rb, offset, size)) {
             return -EBUSY;
         }
         virtio_mem_notify_unplug(vmem, offset, size);
     } else {
         int ret = 0;
 
         if (vmem->prealloc) {
             void *area = memory_region_get_ram_ptr(&vmem->memdev->mr) + offset;
             int fd = memory_region_get_fd(&vmem->memdev->mr);
             Error *local_err = NULL;
 
             qemu_prealloc_mem(fd, area, size, 1, NULL, &local_err);
             if (local_err) {
                 static bool warned;
 
                 /*
                  * Warn only once, we don't want to fill the log with these
                  * warnings.
                  */
                 if (!warned) {
                     warn_report_err(local_err);
                     warned = true;
                 } else {
                     error_free(local_err);
                 }
                 ret = -EBUSY;
             }
         }
         if (!ret) {
             ret = virtio_mem_notify_plug(vmem, offset, size);
         }
 
         if (ret) {
             /* Could be preallocation or a notifier populated memory. */
             ram_block_discard_range(vmem->memdev->mr.ram_block, offset, size);
             return -EBUSY;
         }
     }
     virtio_mem_set_bitmap(vmem, start_gpa, size, plug);
     return 0;
 }
 
 static int virtio_mem_state_change_request(VirtIOMEM *vmem, uint64_t gpa,
                                            uint16_t nb_blocks, bool plug)
 {
     const uint64_t size = nb_blocks * vmem->block_size;
     int ret;
 
     if (!virtio_mem_valid_range(vmem, gpa, size)) {
         return VIRTIO_MEM_RESP_ERROR;
     }
 
     if (plug && (vmem->size + size > vmem->requested_size)) {
         return VIRTIO_MEM_RESP_NACK;
     }
 
     /* test if really all blocks are in the opposite state */
     if (!virtio_mem_test_bitmap(vmem, gpa, size, !plug)) {
         return VIRTIO_MEM_RESP_ERROR;
     }
 
     ret = virtio_mem_set_block_state(vmem, gpa, size, plug);
     if (ret) {
         return VIRTIO_MEM_RESP_BUSY;
     }
     if (plug) {
         vmem->size += size;
     } else {
         vmem->size -= size;
     }
     notifier_list_notify(&vmem->size_change_notifiers, &vmem->size);
     return VIRTIO_MEM_RESP_ACK;
 }
 
 static void virtio_mem_plug_request(VirtIOMEM *vmem, VirtQueueElement *elem,
                                     struct virtio_mem_req *req)
 {
     const uint64_t gpa = le64_to_cpu(req->u.plug.addr);
     const uint16_t nb_blocks = le16_to_cpu(req->u.plug.nb_blocks);
     uint16_t type;
 
     trace_virtio_mem_plug_request(gpa, nb_blocks);
     type = virtio_mem_state_change_request(vmem, gpa, nb_blocks, true);
     virtio_mem_send_response_simple(vmem, elem, type);
 }
 
 static void virtio_mem_unplug_request(VirtIOMEM *vmem, VirtQueueElement *elem,
                                       struct virtio_mem_req *req)
 {
     const uint64_t gpa = le64_to_cpu(req->u.unplug.addr);
     const uint16_t nb_blocks = le16_to_cpu(req->u.unplug.nb_blocks);
     uint16_t type;
 
     trace_virtio_mem_unplug_request(gpa, nb_blocks);
     type = virtio_mem_state_change_request(vmem, gpa, nb_blocks, false);
     virtio_mem_send_response_simple(vmem, elem, type);
 }
 
 static void virtio_mem_resize_usable_region(VirtIOMEM *vmem,
                                             uint64_t requested_size,
                                             bool can_shrink)
 {
     uint64_t newsize = MIN(memory_region_size(&vmem->memdev->mr),
                            requested_size + VIRTIO_MEM_USABLE_EXTENT);
 
     /* The usable region size always has to be multiples of the block size. */
     newsize = QEMU_ALIGN_UP(newsize, vmem->block_size);
 
     if (!requested_size) {
         newsize = 0;
     }
 
     if (newsize < vmem->usable_region_size && !can_shrink) {
         return;
     }
 
     trace_virtio_mem_resized_usable_region(vmem->usable_region_size, newsize);
     vmem->usable_region_size = newsize;
 }
 
 static int virtio_mem_unplug_all(VirtIOMEM *vmem)
 {
     RAMBlock *rb = vmem->memdev->mr.ram_block;
 
     if (virtio_mem_is_busy()) {
         return -EBUSY;
     }
 
     if (ram_block_discard_range(rb, 0, qemu_ram_get_used_length(rb))) {
         return -EBUSY;
     }
     virtio_mem_notify_unplug_all(vmem);
 
     bitmap_clear(vmem->bitmap, 0, vmem->bitmap_size);
     if (vmem->size) {
         vmem->size = 0;
         notifier_list_notify(&vmem->size_change_notifiers, &vmem->size);
     }
     trace_virtio_mem_unplugged_all();
     virtio_mem_resize_usable_region(vmem, vmem->requested_size, true);
     return 0;
 }
 
 static void virtio_mem_unplug_all_request(VirtIOMEM *vmem,
                                           VirtQueueElement *elem)
 {
     trace_virtio_mem_unplug_all_request();
     if (virtio_mem_unplug_all(vmem)) {
         virtio_mem_send_response_simple(vmem, elem, VIRTIO_MEM_RESP_BUSY);
     } else {
         virtio_mem_send_response_simple(vmem, elem, VIRTIO_MEM_RESP_ACK);
     }
 }
 
 static void virtio_mem_state_request(VirtIOMEM *vmem, VirtQueueElement *elem,
                                      struct virtio_mem_req *req)
 {
     const uint16_t nb_blocks = le16_to_cpu(req->u.state.nb_blocks);
     const uint64_t gpa = le64_to_cpu(req->u.state.addr);
     const uint64_t size = nb_blocks * vmem->block_size;
     struct virtio_mem_resp resp = {
         .type = cpu_to_le16(VIRTIO_MEM_RESP_ACK),
     };
 
     trace_virtio_mem_state_request(gpa, nb_blocks);
     if (!virtio_mem_valid_range(vmem, gpa, size)) {
         virtio_mem_send_response_simple(vmem, elem, VIRTIO_MEM_RESP_ERROR);
         return;
     }
 
     if (virtio_mem_test_bitmap(vmem, gpa, size, true)) {
         resp.u.state.state = cpu_to_le16(VIRTIO_MEM_STATE_PLUGGED);
     } else if (virtio_mem_test_bitmap(vmem, gpa, size, false)) {
         resp.u.state.state = cpu_to_le16(VIRTIO_MEM_STATE_UNPLUGGED);
     } else {
         resp.u.state.state = cpu_to_le16(VIRTIO_MEM_STATE_MIXED);
     }
     trace_virtio_mem_state_response(le16_to_cpu(resp.u.state.state));
     virtio_mem_send_response(vmem, elem, &resp);
 }
 
 static void virtio_mem_handle_request(VirtIODevice *vdev, VirtQueue *vq)
 {
     const int len = sizeof(struct virtio_mem_req);
     VirtIOMEM *vmem = VIRTIO_MEM(vdev);
     VirtQueueElement *elem;
     struct virtio_mem_req req;
     uint16_t type;
 
     while (true) {
         elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
         if (!elem) {
             return;
         }
 
         if (iov_to_buf(elem->out_sg, elem->out_num, 0, &req, len) < len) {
             virtio_error(vdev, "virtio-mem protocol violation: invalid request"
                          " size: %d", len);
             virtqueue_detach_element(vq, elem, 0);
             g_free(elem);
             return;
         }
 
         if (iov_size(elem->in_sg, elem->in_num) <
             sizeof(struct virtio_mem_resp)) {
             virtio_error(vdev, "virtio-mem protocol violation: not enough space"
                          " for response: %zu",
                          iov_size(elem->in_sg, elem->in_num));
             virtqueue_detach_element(vq, elem, 0);
             g_free(elem);
             return;
         }
 
         type = le16_to_cpu(req.type);
         switch (type) {
         case VIRTIO_MEM_REQ_PLUG:
             virtio_mem_plug_request(vmem, elem, &req);
             break;
         case VIRTIO_MEM_REQ_UNPLUG:
             virtio_mem_unplug_request(vmem, elem, &req);
             break;
         case VIRTIO_MEM_REQ_UNPLUG_ALL:
             virtio_mem_unplug_all_request(vmem, elem);
             break;
         case VIRTIO_MEM_REQ_STATE:
             virtio_mem_state_request(vmem, elem, &req);
             break;
         default:
             virtio_error(vdev, "virtio-mem protocol violation: unknown request"
                          " type: %d", type);
             virtqueue_detach_element(vq, elem, 0);
             g_free(elem);
             return;
         }
 
         g_free(elem);
     }
 }
 
 static void virtio_mem_get_config(VirtIODevice *vdev, uint8_t *config_data)
 {
     VirtIOMEM *vmem = VIRTIO_MEM(vdev);
     struct virtio_mem_config *config = (void *) config_data;
 
     config->block_size = cpu_to_le64(vmem->block_size);
     config->node_id = cpu_to_le16(vmem->node);
     config->requested_size = cpu_to_le64(vmem->requested_size);
     config->plugged_size = cpu_to_le64(vmem->size);
     config->addr = cpu_to_le64(vmem->addr);
     config->region_size = cpu_to_le64(memory_region_size(&vmem->memdev->mr));
     config->usable_region_size = cpu_to_le64(vmem->usable_region_size);
 }
 
 static uint64_t virtio_mem_get_features(VirtIODevice *vdev, uint64_t features,
                                         Error **errp)
 {
     MachineState *ms = MACHINE(qdev_get_machine());
     VirtIOMEM *vmem = VIRTIO_MEM(vdev);
 
     if (ms->numa_state) {
 #if defined(CONFIG_ACPI)
         virtio_add_feature(&features, VIRTIO_MEM_F_ACPI_PXM);
 #endif
     }
     assert(vmem->unplugged_inaccessible != ON_OFF_AUTO_AUTO);
     if (vmem->unplugged_inaccessible == ON_OFF_AUTO_ON) {
         virtio_add_feature(&features, VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE);
     }
     return features;
 }
 
 static int virtio_mem_validate_features(VirtIODevice *vdev)
 {
     if (virtio_host_has_feature(vdev, VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE) &&
         !virtio_vdev_has_feature(vdev, VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE)) {
         return -EFAULT;
     }
     return 0;
 }
 
 static void virtio_mem_system_reset(void *opaque)
 {
     VirtIOMEM *vmem = VIRTIO_MEM(opaque);
 
     /*
      * During usual resets, we will unplug all memory and shrink the usable
      * region size. This is, however, not possible in all scenarios. Then,
      * the guest has to deal with this manually (VIRTIO_MEM_REQ_UNPLUG_ALL).
      */
     virtio_mem_unplug_all(vmem);
 }
 
 static void virtio_mem_device_realize(DeviceState *dev, Error **errp)
 {
     MachineState *ms = MACHINE(qdev_get_machine());
     int nb_numa_nodes = ms->numa_state ? ms->numa_state->num_nodes : 0;
     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
     VirtIOMEM *vmem = VIRTIO_MEM(dev);
     uint64_t page_size;
     RAMBlock *rb;
     int ret;
 
     if (!vmem->memdev) {
         error_setg(errp, "'%s' property is not set", VIRTIO_MEM_MEMDEV_PROP);
         return;
     } else if (host_memory_backend_is_mapped(vmem->memdev)) {
         error_setg(errp, "'%s' property specifies a busy memdev: %s",
                    VIRTIO_MEM_MEMDEV_PROP,
                    object_get_canonical_path_component(OBJECT(vmem->memdev)));
         return;
     } else if (!memory_region_is_ram(&vmem->memdev->mr) ||
         memory_region_is_rom(&vmem->memdev->mr) ||
         !vmem->memdev->mr.ram_block) {
         error_setg(errp, "'%s' property specifies an unsupported memdev",
                    VIRTIO_MEM_MEMDEV_PROP);
         return;
     }
 
     if ((nb_numa_nodes && vmem->node >= nb_numa_nodes) ||
         (!nb_numa_nodes && vmem->node)) {
         error_setg(errp, "'%s' property has value '%" PRIu32 "', which exceeds"
                    "the number of numa nodes: %d", VIRTIO_MEM_NODE_PROP,
                    vmem->node, nb_numa_nodes ? nb_numa_nodes : 1);
         return;
     }
 
     if (enable_mlock) {
         error_setg(errp, "Incompatible with mlock");
         return;
     }
 
     rb = vmem->memdev->mr.ram_block;
     page_size = qemu_ram_pagesize(rb);
 
 #if defined(VIRTIO_MEM_HAS_LEGACY_GUESTS)
     switch (vmem->unplugged_inaccessible) {
     case ON_OFF_AUTO_AUTO:
         if (virtio_mem_has_shared_zeropage(rb)) {
             vmem->unplugged_inaccessible = ON_OFF_AUTO_OFF;
         } else {
             vmem->unplugged_inaccessible = ON_OFF_AUTO_ON;
         }
         break;
     case ON_OFF_AUTO_OFF:
         if (!virtio_mem_has_shared_zeropage(rb)) {
             warn_report("'%s' property set to 'off' with a memdev that does"
                         " not support the shared zeropage.",
                         VIRTIO_MEM_UNPLUGGED_INACCESSIBLE_PROP);
         }
         break;
     default:
         break;
     }
 #else /* VIRTIO_MEM_HAS_LEGACY_GUESTS */
     vmem->unplugged_inaccessible = ON_OFF_AUTO_ON;
 #endif /* VIRTIO_MEM_HAS_LEGACY_GUESTS */
 
     /*
      * If the block size wasn't configured by the user, use a sane default. This
      * allows using hugetlbfs backends of any page size without manual
      * intervention.
      */
     if (!vmem->block_size) {
         vmem->block_size = virtio_mem_default_block_size(rb);
     }
 
     if (vmem->block_size < page_size) {
         error_setg(errp, "'%s' property has to be at least the page size (0x%"
                    PRIx64 ")", VIRTIO_MEM_BLOCK_SIZE_PROP, page_size);
         return;
     } else if (vmem->block_size < virtio_mem_default_block_size(rb)) {
         warn_report("'%s' property is smaller than the default block size (%"
                     PRIx64 " MiB)", VIRTIO_MEM_BLOCK_SIZE_PROP,
                     virtio_mem_default_block_size(rb) / MiB);
     }
     if (!QEMU_IS_ALIGNED(vmem->requested_size, vmem->block_size)) {
         error_setg(errp, "'%s' property has to be multiples of '%s' (0x%" PRIx64
                    ")", VIRTIO_MEM_REQUESTED_SIZE_PROP,
                    VIRTIO_MEM_BLOCK_SIZE_PROP, vmem->block_size);
         return;
     } else if (!QEMU_IS_ALIGNED(vmem->addr, vmem->block_size)) {
         error_setg(errp, "'%s' property has to be multiples of '%s' (0x%" PRIx64
                    ")", VIRTIO_MEM_ADDR_PROP, VIRTIO_MEM_BLOCK_SIZE_PROP,
                    vmem->block_size);
         return;
     } else if (!QEMU_IS_ALIGNED(memory_region_size(&vmem->memdev->mr),
                                 vmem->block_size)) {
         error_setg(errp, "'%s' property memdev size has to be multiples of"
                    "'%s' (0x%" PRIx64 ")", VIRTIO_MEM_MEMDEV_PROP,
                    VIRTIO_MEM_BLOCK_SIZE_PROP, vmem->block_size);
         return;
     }
 
     if (ram_block_coordinated_discard_require(true)) {
         error_setg(errp, "Discarding RAM is disabled");
         return;
     }
 
     ret = ram_block_discard_range(rb, 0, qemu_ram_get_used_length(rb));
     if (ret) {
         error_setg_errno(errp, -ret, "Unexpected error discarding RAM");
         ram_block_coordinated_discard_require(false);
         return;
     }
 
     virtio_mem_resize_usable_region(vmem, vmem->requested_size, true);
 
     vmem->bitmap_size = memory_region_size(&vmem->memdev->mr) /
                         vmem->block_size;
     vmem->bitmap = bitmap_new(vmem->bitmap_size);
 
     virtio_init(vdev, VIRTIO_ID_MEM, sizeof(struct virtio_mem_config));
     vmem->vq = virtio_add_queue(vdev, 128, virtio_mem_handle_request);
 
     host_memory_backend_set_mapped(vmem->memdev, true);
     vmstate_register_ram(&vmem->memdev->mr, DEVICE(vmem));
     qemu_register_reset(virtio_mem_system_reset, vmem);
 
     /*
      * Set ourselves as RamDiscardManager before the plug handler maps the
      * memory region and exposes it via an address space.
      */
     memory_region_set_ram_discard_manager(&vmem->memdev->mr,
                                           RAM_DISCARD_MANAGER(vmem));
 }
 
 static void virtio_mem_device_unrealize(DeviceState *dev)
 {
     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
     VirtIOMEM *vmem = VIRTIO_MEM(dev);
 
     /*
      * The unplug handler unmapped the memory region, it cannot be
      * found via an address space anymore. Unset ourselves.
      */
     memory_region_set_ram_discard_manager(&vmem->memdev->mr, NULL);
     qemu_unregister_reset(virtio_mem_system_reset, vmem);
     vmstate_unregister_ram(&vmem->memdev->mr, DEVICE(vmem));
     host_memory_backend_set_mapped(vmem->memdev, false);
     virtio_del_queue(vdev, 0);
     virtio_cleanup(vdev);
     g_free(vmem->bitmap);
     ram_block_coordinated_discard_require(false);
 }
 
 static int virtio_mem_discard_range_cb(const VirtIOMEM *vmem, void *arg,
                                        uint64_t offset, uint64_t size)
 {
     RAMBlock *rb = vmem->memdev->mr.ram_block;
 
     return ram_block_discard_range(rb, offset, size) ? -EINVAL : 0;
 }
 
 static int virtio_mem_restore_unplugged(VirtIOMEM *vmem)
 {
     /* Make sure all memory is really discarded after migration. */
     return virtio_mem_for_each_unplugged_range(vmem, NULL,
                                                virtio_mem_discard_range_cb);
 }
 
 static int virtio_mem_post_load(void *opaque, int version_id)
 {
     VirtIOMEM *vmem = VIRTIO_MEM(opaque);
     RamDiscardListener *rdl;
     int ret;
 
     /*
      * We started out with all memory discarded and our memory region is mapped
      * into an address space. Replay, now that we updated the bitmap.
      */
     QLIST_FOREACH(rdl, &vmem->rdl_list, next) {
         ret = virtio_mem_for_each_plugged_section(vmem, rdl->section, rdl,
                                                  virtio_mem_notify_populate_cb);
         if (ret) {
             return ret;
         }
     }
 
     if (migration_in_incoming_postcopy()) {
         return 0;
     }
 
     return virtio_mem_restore_unplugged(vmem);
 }
 
 typedef struct VirtIOMEMMigSanityChecks {
     VirtIOMEM *parent;
     uint64_t addr;
     uint64_t region_size;
     uint64_t block_size;
     uint32_t node;
 } VirtIOMEMMigSanityChecks;
 
 static int virtio_mem_mig_sanity_checks_pre_save(void *opaque)
 {
     VirtIOMEMMigSanityChecks *tmp = opaque;
     VirtIOMEM *vmem = tmp->parent;
 
     tmp->addr = vmem->addr;
     tmp->region_size = memory_region_size(&vmem->memdev->mr);
     tmp->block_size = vmem->block_size;
     tmp->node = vmem->node;
     return 0;
 }
 
 static int virtio_mem_mig_sanity_checks_post_load(void *opaque, int version_id)
 {
     VirtIOMEMMigSanityChecks *tmp = opaque;
     VirtIOMEM *vmem = tmp->parent;
     const uint64_t new_region_size = memory_region_size(&vmem->memdev->mr);
 
     if (tmp->addr != vmem->addr) {
         error_report("Property '%s' changed from 0x%" PRIx64 " to 0x%" PRIx64,
                      VIRTIO_MEM_ADDR_PROP, tmp->addr, vmem->addr);
         return -EINVAL;
     }
     /*
      * Note: Preparation for resizeable memory regions. The maximum size
      * of the memory region must not change during migration.
      */
     if (tmp->region_size != new_region_size) {
         error_report("Property '%s' size changed from 0x%" PRIx64 " to 0x%"
                      PRIx64, VIRTIO_MEM_MEMDEV_PROP, tmp->region_size,
                      new_region_size);
         return -EINVAL;
     }
     if (tmp->block_size != vmem->block_size) {
         error_report("Property '%s' changed from 0x%" PRIx64 " to 0x%" PRIx64,
                      VIRTIO_MEM_BLOCK_SIZE_PROP, tmp->block_size,
                      vmem->block_size);
         return -EINVAL;
     }
     if (tmp->node != vmem->node) {
         error_report("Property '%s' changed from %" PRIu32 " to %" PRIu32,
                      VIRTIO_MEM_NODE_PROP, tmp->node, vmem->node);
         return -EINVAL;
     }
     return 0;
 }
 
 static const VMStateDescription vmstate_virtio_mem_sanity_checks = {
     .name = "virtio-mem-device/sanity-checks",
     .pre_save = virtio_mem_mig_sanity_checks_pre_save,
     .post_load = virtio_mem_mig_sanity_checks_post_load,
     .fields = (VMStateField[]) {
         VMSTATE_UINT64(addr, VirtIOMEMMigSanityChecks),
         VMSTATE_UINT64(region_size, VirtIOMEMMigSanityChecks),
         VMSTATE_UINT64(block_size, VirtIOMEMMigSanityChecks),
         VMSTATE_UINT32(node, VirtIOMEMMigSanityChecks),
         VMSTATE_END_OF_LIST(),
     },
 };
 
 static const VMStateDescription vmstate_virtio_mem_device = {
     .name = "virtio-mem-device",
     .minimum_version_id = 1,
     .version_id = 1,
     .priority = MIG_PRI_VIRTIO_MEM,
     .post_load = virtio_mem_post_load,
     .fields = (VMStateField[]) {
         VMSTATE_WITH_TMP(VirtIOMEM, VirtIOMEMMigSanityChecks,
                          vmstate_virtio_mem_sanity_checks),
         VMSTATE_UINT64(usable_region_size, VirtIOMEM),
         VMSTATE_UINT64(size, VirtIOMEM),
         VMSTATE_UINT64(requested_size, VirtIOMEM),
         VMSTATE_BITMAP(bitmap, VirtIOMEM, 0, bitmap_size),
         VMSTATE_END_OF_LIST()
     },
 };
 
 static const VMStateDescription vmstate_virtio_mem = {
     .name = "virtio-mem",
     .minimum_version_id = 1,
     .version_id = 1,
     .fields = (VMStateField[]) {
         VMSTATE_VIRTIO_DEVICE,
         VMSTATE_END_OF_LIST()
     },
 };
 
 static void virtio_mem_fill_device_info(const VirtIOMEM *vmem,
                                         VirtioMEMDeviceInfo *vi)
 {
     vi->memaddr = vmem->addr;
     vi->node = vmem->node;
     vi->requested_size = vmem->requested_size;
     vi->size = vmem->size;
     vi->max_size = memory_region_size(&vmem->memdev->mr);
     vi->block_size = vmem->block_size;
     vi->memdev = object_get_canonical_path(OBJECT(vmem->memdev));
 }
 
 static MemoryRegion *virtio_mem_get_memory_region(VirtIOMEM *vmem, Error **errp)
 {
     if (!vmem->memdev) {
         error_setg(errp, "'%s' property must be set", VIRTIO_MEM_MEMDEV_PROP);
         return NULL;
     }
 
     return &vmem->memdev->mr;
 }
 
 static void virtio_mem_add_size_change_notifier(VirtIOMEM *vmem,
                                                 Notifier *notifier)
 {
     notifier_list_add(&vmem->size_change_notifiers, notifier);
 }
 
 static void virtio_mem_remove_size_change_notifier(VirtIOMEM *vmem,
                                                    Notifier *notifier)
 {
     notifier_remove(notifier);
 }
 
 static void virtio_mem_get_size(Object *obj, Visitor *v, const char *name,
                                 void *opaque, Error **errp)
 {
     const VirtIOMEM *vmem = VIRTIO_MEM(obj);
     uint64_t value = vmem->size;
 
     visit_type_size(v, name, &value, errp);
 }
 
 static void virtio_mem_get_requested_size(Object *obj, Visitor *v,
                                           const char *name, void *opaque,
                                           Error **errp)
 {
     const VirtIOMEM *vmem = VIRTIO_MEM(obj);
     uint64_t value = vmem->requested_size;
 
     visit_type_size(v, name, &value, errp);
 }
 
 static void virtio_mem_set_requested_size(Object *obj, Visitor *v,
                                           const char *name, void *opaque,
                                           Error **errp)
 {
     VirtIOMEM *vmem = VIRTIO_MEM(obj);
     Error *err = NULL;
     uint64_t value;
 
     visit_type_size(v, name, &value, &err);
     if (err) {
         error_propagate(errp, err);
         return;
     }
 
     /*
      * The block size and memory backend are not fixed until the device was
      * realized. realize() will verify these properties then.
      */
     if (DEVICE(obj)->realized) {
         if (!QEMU_IS_ALIGNED(value, vmem->block_size)) {
             error_setg(errp, "'%s' has to be multiples of '%s' (0x%" PRIx64
                        ")", name, VIRTIO_MEM_BLOCK_SIZE_PROP,
                        vmem->block_size);
             return;
         } else if (value > memory_region_size(&vmem->memdev->mr)) {
             error_setg(errp, "'%s' cannot exceed the memory backend size"
                        "(0x%" PRIx64 ")", name,
                        memory_region_size(&vmem->memdev->mr));
             return;
         }
 
         if (value != vmem->requested_size) {
             virtio_mem_resize_usable_region(vmem, value, false);
             vmem->requested_size = value;
         }
         /*
          * Trigger a config update so the guest gets notified. We trigger
          * even if the size didn't change (especially helpful for debugging).
          */
         virtio_notify_config(VIRTIO_DEVICE(vmem));
     } else {
         vmem->requested_size = value;
     }
 }
 
 static void virtio_mem_get_block_size(Object *obj, Visitor *v, const char *name,
                                       void *opaque, Error **errp)
 {
     const VirtIOMEM *vmem = VIRTIO_MEM(obj);
     uint64_t value = vmem->block_size;
 
     /*
      * If not configured by the user (and we're not realized yet), use the
      * default block size we would use with the current memory backend.
      */
     if (!value) {
         if (vmem->memdev && memory_region_is_ram(&vmem->memdev->mr)) {
             value = virtio_mem_default_block_size(vmem->memdev->mr.ram_block);
         } else {
             value = virtio_mem_thp_size();
         }
     }
 
     visit_type_size(v, name, &value, errp);
 }
 
 static void virtio_mem_set_block_size(Object *obj, Visitor *v, const char *name,
                                       void *opaque, Error **errp)
 {
     VirtIOMEM *vmem = VIRTIO_MEM(obj);
     Error *err = NULL;
     uint64_t value;
 
     if (DEVICE(obj)->realized) {
         error_setg(errp, "'%s' cannot be changed", name);
         return;
     }
 
     visit_type_size(v, name, &value, &err);
     if (err) {
         error_propagate(errp, err);
         return;
     }
 
     if (value < VIRTIO_MEM_MIN_BLOCK_SIZE) {
         error_setg(errp, "'%s' property has to be at least 0x%" PRIx32, name,
                    VIRTIO_MEM_MIN_BLOCK_SIZE);
         return;
     } else if (!is_power_of_2(value)) {
         error_setg(errp, "'%s' property has to be a power of two", name);
         return;
     }
     vmem->block_size = value;
 }
 
 static void virtio_mem_instance_init(Object *obj)
 {
     VirtIOMEM *vmem = VIRTIO_MEM(obj);
 
     notifier_list_init(&vmem->size_change_notifiers);
     QLIST_INIT(&vmem->rdl_list);
 
     object_property_add(obj, VIRTIO_MEM_SIZE_PROP, "size", virtio_mem_get_size,
                         NULL, NULL, NULL);
     object_property_add(obj, VIRTIO_MEM_REQUESTED_SIZE_PROP, "size",
                         virtio_mem_get_requested_size,
                         virtio_mem_set_requested_size, NULL, NULL);
     object_property_add(obj, VIRTIO_MEM_BLOCK_SIZE_PROP, "size",
                         virtio_mem_get_block_size, virtio_mem_set_block_size,
                         NULL, NULL);
 }
 
 static Property virtio_mem_properties[] = {
     DEFINE_PROP_UINT64(VIRTIO_MEM_ADDR_PROP, VirtIOMEM, addr, 0),
     DEFINE_PROP_UINT32(VIRTIO_MEM_NODE_PROP, VirtIOMEM, node, 0),
     DEFINE_PROP_BOOL(VIRTIO_MEM_PREALLOC_PROP, VirtIOMEM, prealloc, false),
     DEFINE_PROP_LINK(VIRTIO_MEM_MEMDEV_PROP, VirtIOMEM, memdev,
                      TYPE_MEMORY_BACKEND, HostMemoryBackend *),
 #if defined(VIRTIO_MEM_HAS_LEGACY_GUESTS)
     DEFINE_PROP_ON_OFF_AUTO(VIRTIO_MEM_UNPLUGGED_INACCESSIBLE_PROP, VirtIOMEM,
                             unplugged_inaccessible, ON_OFF_AUTO_AUTO),
 #endif
     DEFINE_PROP_END_OF_LIST(),
 };
 
 static uint64_t virtio_mem_rdm_get_min_granularity(const RamDiscardManager *rdm,
                                                    const MemoryRegion *mr)
 {
     const VirtIOMEM *vmem = VIRTIO_MEM(rdm);
 
     g_assert(mr == &vmem->memdev->mr);
     return vmem->block_size;
 }
 
 static bool virtio_mem_rdm_is_populated(const RamDiscardManager *rdm,
                                         const MemoryRegionSection *s)
 {
     const VirtIOMEM *vmem = VIRTIO_MEM(rdm);
     uint64_t start_gpa = vmem->addr + s->offset_within_region;
     uint64_t end_gpa = start_gpa + int128_get64(s->size);
 
     g_assert(s->mr == &vmem->memdev->mr);
 
     start_gpa = QEMU_ALIGN_DOWN(start_gpa, vmem->block_size);
     end_gpa = QEMU_ALIGN_UP(end_gpa, vmem->block_size);
 
     if (!virtio_mem_valid_range(vmem, start_gpa, end_gpa - start_gpa)) {
         return false;
     }
 
     return virtio_mem_test_bitmap(vmem, start_gpa, end_gpa - start_gpa, true);
 }
 
 struct VirtIOMEMReplayData {
     void *fn;
     void *opaque;
 };
 
 static int virtio_mem_rdm_replay_populated_cb(MemoryRegionSection *s, void *arg)
 {
     struct VirtIOMEMReplayData *data = arg;
 
     return ((ReplayRamPopulate)data->fn)(s, data->opaque);
 }
 
 static int virtio_mem_rdm_replay_populated(const RamDiscardManager *rdm,
                                            MemoryRegionSection *s,
                                            ReplayRamPopulate replay_fn,
                                            void *opaque)
 {
     const VirtIOMEM *vmem = VIRTIO_MEM(rdm);
     struct VirtIOMEMReplayData data = {
         .fn = replay_fn,
         .opaque = opaque,
     };
 
     g_assert(s->mr == &vmem->memdev->mr);
     return virtio_mem_for_each_plugged_section(vmem, s, &data,
                                             virtio_mem_rdm_replay_populated_cb);
 }
 
 static int virtio_mem_rdm_replay_discarded_cb(MemoryRegionSection *s,
                                               void *arg)
 {
     struct VirtIOMEMReplayData *data = arg;
 
     ((ReplayRamDiscard)data->fn)(s, data->opaque);
     return 0;
 }
 
 static void virtio_mem_rdm_replay_discarded(const RamDiscardManager *rdm,
                                             MemoryRegionSection *s,
                                             ReplayRamDiscard replay_fn,
                                             void *opaque)
 {
     const VirtIOMEM *vmem = VIRTIO_MEM(rdm);
     struct VirtIOMEMReplayData data = {
         .fn = replay_fn,
         .opaque = opaque,
     };
 
     g_assert(s->mr == &vmem->memdev->mr);
     virtio_mem_for_each_unplugged_section(vmem, s, &data,
                                           virtio_mem_rdm_replay_discarded_cb);
 }
 
 static void virtio_mem_rdm_register_listener(RamDiscardManager *rdm,
                                              RamDiscardListener *rdl,
                                              MemoryRegionSection *s)
 {
     VirtIOMEM *vmem = VIRTIO_MEM(rdm);
     int ret;
 
     g_assert(s->mr == &vmem->memdev->mr);
     rdl->section = memory_region_section_new_copy(s);
 
     QLIST_INSERT_HEAD(&vmem->rdl_list, rdl, next);
     ret = virtio_mem_for_each_plugged_section(vmem, rdl->section, rdl,
                                               virtio_mem_notify_populate_cb);
     if (ret) {
         error_report("%s: Replaying plugged ranges failed: %s", __func__,
                      strerror(-ret));
     }
 }
 
 static void virtio_mem_rdm_unregister_listener(RamDiscardManager *rdm,
                                                RamDiscardListener *rdl)
 {
     VirtIOMEM *vmem = VIRTIO_MEM(rdm);
 
     g_assert(rdl->section->mr == &vmem->memdev->mr);
     if (vmem->size) {
         if (rdl->double_discard_supported) {
             rdl->notify_discard(rdl, rdl->section);
         } else {
             virtio_mem_for_each_plugged_section(vmem, rdl->section, rdl,
                                                 virtio_mem_notify_discard_cb);
         }
     }
 
     memory_region_section_free_copy(rdl->section);
     rdl->section = NULL;
     QLIST_REMOVE(rdl, next);
 }
 
 static void virtio_mem_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
     VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
     VirtIOMEMClass *vmc = VIRTIO_MEM_CLASS(klass);
     RamDiscardManagerClass *rdmc = RAM_DISCARD_MANAGER_CLASS(klass);
 
     device_class_set_props(dc, virtio_mem_properties);
     dc->vmsd = &vmstate_virtio_mem;
 
     set_bit(DEVICE_CATEGORY_MISC, dc->categories);
     vdc->realize = virtio_mem_device_realize;
     vdc->unrealize = virtio_mem_device_unrealize;
     vdc->get_config = virtio_mem_get_config;
     vdc->get_features = virtio_mem_get_features;
     vdc->validate_features = virtio_mem_validate_features;
     vdc->vmsd = &vmstate_virtio_mem_device;
 
     vmc->fill_device_info = virtio_mem_fill_device_info;
     vmc->get_memory_region = virtio_mem_get_memory_region;
     vmc->add_size_change_notifier = virtio_mem_add_size_change_notifier;
     vmc->remove_size_change_notifier = virtio_mem_remove_size_change_notifier;
 
     rdmc->get_min_granularity = virtio_mem_rdm_get_min_granularity;
     rdmc->is_populated = virtio_mem_rdm_is_populated;
     rdmc->replay_populated = virtio_mem_rdm_replay_populated;
     rdmc->replay_discarded = virtio_mem_rdm_replay_discarded;
     rdmc->register_listener = virtio_mem_rdm_register_listener;
     rdmc->unregister_listener = virtio_mem_rdm_unregister_listener;
 }
 
 static const TypeInfo virtio_mem_info = {
     .name = TYPE_VIRTIO_MEM,
     .parent = TYPE_VIRTIO_DEVICE,
     .instance_size = sizeof(VirtIOMEM),
     .instance_init = virtio_mem_instance_init,
     .class_init = virtio_mem_class_init,
     .class_size = sizeof(VirtIOMEMClass),
     .interfaces = (InterfaceInfo[]) {
         { TYPE_RAM_DISCARD_MANAGER },
         { }
     },
 };
 
 static void virtio_register_types(void)
 {
     type_register_static(&virtio_mem_info);
 }
 
 type_init(virtio_register_types)