virtio-balloon: add support for page poison reporting and free page reporting

index 9375ca2a70de..af0a6b59dab2 100644
@@ -47,8 +47,15 @@ struct virtio_balloon_config {
 	uint32_t num_pages;
 	/* Number of pages we've actually got in balloon. */
 	uint32_t actual;
-	/* Free page report command id, readonly by guest */
-	uint32_t free_page_report_cmd_id;
+	/*
+	 * Free page hint command id, readonly by guest.
+	 * Was previously name free_page_report_cmd_id so we
+	 * need to carry that name for legacy support.
+	 */
+	union {
+		uint32_t free_page_hint_cmd_id;
+		uint32_t free_page_report_cmd_id;	/* deprecated */
+	};
 	/* Stores PAGE_POISON if page poisoning is in use */
 	uint32_t poison_val;
 };

index af0a6b59dab2..af3b7a1fa263 100644
@@ -36,6 +36,7 @@
 #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM	2 /* Deflate balloon on OOM */
 #define VIRTIO_BALLOON_F_FREE_PAGE_HINT	3 /* VQ to report free pages */
 #define VIRTIO_BALLOON_F_PAGE_POISON	4 /* Guest is using page poisoning */
+#define VIRTIO_BALLOON_F_REPORTING	5 /* Page reporting virtqueue */
 
 /* Size of a PFN in the balloon interface. */
 #define VIRTIO_BALLOON_PFN_SHIFT 12

index a4729f7fc930..a209706b4d8d 100644
@@ -466,21 +466,21 @@ static bool get_free_page_hints(VirtIOBalloon *dev)
             ret = false;
             goto out;
         }
-        if (id == dev->free_page_report_cmd_id) {
-            dev->free_page_report_status = FREE_PAGE_REPORT_S_START;
+        if (id == dev->free_page_hint_cmd_id) {
+            dev->free_page_hint_status = FREE_PAGE_HINT_S_START;
         } else {
             /*
              * Stop the optimization only when it has started. This
              * avoids a stale stop sign for the previous command.
              */
-            if (dev->free_page_report_status == FREE_PAGE_REPORT_S_START) {
-                dev->free_page_report_status = FREE_PAGE_REPORT_S_STOP;
+            if (dev->free_page_hint_status == FREE_PAGE_HINT_S_START) {
+                dev->free_page_hint_status = FREE_PAGE_HINT_S_STOP;
             }
         }
     }
 
     if (elem->in_num) {
-        if (dev->free_page_report_status == FREE_PAGE_REPORT_S_START) {
+        if (dev->free_page_hint_status == FREE_PAGE_HINT_S_START) {
             qemu_guest_free_page_hint(elem->in_sg[0].iov_base,
                                       elem->in_sg[0].iov_len);
         }

@@ -506,11 +506,11 @@ static void virtio_ballloon_get_free_page_hints(void *opaque)
         qemu_mutex_unlock(&dev->free_page_lock);
         virtio_notify(vdev, vq);
       /*
-       * Start to poll the vq once the reporting started. Otherwise, continue
+       * Start to poll the vq once the hinting started. Otherwise, continue
        * only when there are entries on the vq, which need to be given back.
        */
     } while (continue_to_get_hints ||
-             dev->free_page_report_status == FREE_PAGE_REPORT_S_START);
+             dev->free_page_hint_status == FREE_PAGE_HINT_S_START);
     virtio_queue_set_notification(vq, 1);
 }
 

@@ -531,14 +531,14 @@ static void virtio_balloon_free_page_start(VirtIOBalloon *s)
         return;
     }
 
-    if (s->free_page_report_cmd_id == UINT_MAX) {
-        s->free_page_report_cmd_id =
-                       VIRTIO_BALLOON_FREE_PAGE_REPORT_CMD_ID_MIN;
+    if (s->free_page_hint_cmd_id == UINT_MAX) {
+        s->free_page_hint_cmd_id =
+                       VIRTIO_BALLOON_FREE_PAGE_HINT_CMD_ID_MIN;
     } else {
-        s->free_page_report_cmd_id++;
+        s->free_page_hint_cmd_id++;
     }
 
-    s->free_page_report_status = FREE_PAGE_REPORT_S_REQUESTED;
+    s->free_page_hint_status = FREE_PAGE_HINT_S_REQUESTED;
     virtio_notify_config(vdev);
 }
 

@@ -546,18 +546,18 @@ static void virtio_balloon_free_page_stop(VirtIOBalloon *s)
 {
     VirtIODevice *vdev = VIRTIO_DEVICE(s);
 
-    if (s->free_page_report_status != FREE_PAGE_REPORT_S_STOP) {
+    if (s->free_page_hint_status != FREE_PAGE_HINT_S_STOP) {
         /*
          * The lock also guarantees us that the
          * virtio_ballloon_get_free_page_hints exits after the
-         * free_page_report_status is set to S_STOP.
+         * free_page_hint_status is set to S_STOP.
          */
         qemu_mutex_lock(&s->free_page_lock);
         /*
-         * The guest hasn't done the reporting, so host sends a notification
-         * to the guest to actively stop the reporting.
+         * The guest isn't done hinting, so send a notification
+         * to the guest to actively stop the hinting.
          */
-        s->free_page_report_status = FREE_PAGE_REPORT_S_STOP;
+        s->free_page_hint_status = FREE_PAGE_HINT_S_STOP;
         qemu_mutex_unlock(&s->free_page_lock);
         virtio_notify_config(vdev);
     }

@@ -567,15 +567,15 @@ static void virtio_balloon_free_page_done(VirtIOBalloon *s)
 {
     VirtIODevice *vdev = VIRTIO_DEVICE(s);
 
-    s->free_page_report_status = FREE_PAGE_REPORT_S_DONE;
+    s->free_page_hint_status = FREE_PAGE_HINT_S_DONE;
     virtio_notify_config(vdev);
 }
 
 static int
-virtio_balloon_free_page_report_notify(NotifierWithReturn *n, void *data)
+virtio_balloon_free_page_hint_notify(NotifierWithReturn *n, void *data)
 {
     VirtIOBalloon *dev = container_of(n, VirtIOBalloon,
-                                      free_page_report_notify);
+                                      free_page_hint_notify);
     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
     PrecopyNotifyData *pnd = data;
 

@@ -624,7 +624,7 @@ static size_t virtio_balloon_config_size(VirtIOBalloon *s)
     if (virtio_has_feature(features, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
         return offsetof(struct virtio_balloon_config, poison_val);
     }
-    return offsetof(struct virtio_balloon_config, free_page_report_cmd_id);
+    return offsetof(struct virtio_balloon_config, free_page_hint_cmd_id);
 }
 
 static void virtio_balloon_get_config(VirtIODevice *vdev, uint8_t *config_data)

@@ -635,14 +635,14 @@ static void virtio_balloon_get_config(VirtIODevice *vdev, uint8_t *config_data)
     config.num_pages = cpu_to_le32(dev->num_pages);
     config.actual = cpu_to_le32(dev->actual);
 
-    if (dev->free_page_report_status == FREE_PAGE_REPORT_S_REQUESTED) {
-        config.free_page_report_cmd_id =
-                       cpu_to_le32(dev->free_page_report_cmd_id);
-    } else if (dev->free_page_report_status == FREE_PAGE_REPORT_S_STOP) {
-        config.free_page_report_cmd_id =
+    if (dev->free_page_hint_status == FREE_PAGE_HINT_S_REQUESTED) {
+        config.free_page_hint_cmd_id =
+                       cpu_to_le32(dev->free_page_hint_cmd_id);
+    } else if (dev->free_page_hint_status == FREE_PAGE_HINT_S_STOP) {
+        config.free_page_hint_cmd_id =
                        cpu_to_le32(VIRTIO_BALLOON_CMD_ID_STOP);
-    } else if (dev->free_page_report_status == FREE_PAGE_REPORT_S_DONE) {
-        config.free_page_report_cmd_id =
+    } else if (dev->free_page_hint_status == FREE_PAGE_HINT_S_DONE) {
+        config.free_page_hint_cmd_id =
                        cpu_to_le32(VIRTIO_BALLOON_CMD_ID_DONE);
     }
 

@@ -743,14 +743,14 @@ static int virtio_balloon_post_load_device(void *opaque, int version_id)
     return 0;
 }
 
-static const VMStateDescription vmstate_virtio_balloon_free_page_report = {
+static const VMStateDescription vmstate_virtio_balloon_free_page_hint = {
     .name = "virtio-balloon-device/free-page-report",
     .version_id = 1,
     .minimum_version_id = 1,
     .needed = virtio_balloon_free_page_support,
     .fields = (VMStateField[]) {
-        VMSTATE_UINT32(free_page_report_cmd_id, VirtIOBalloon),
-        VMSTATE_UINT32(free_page_report_status, VirtIOBalloon),
+        VMSTATE_UINT32(free_page_hint_cmd_id, VirtIOBalloon),
+        VMSTATE_UINT32(free_page_hint_status, VirtIOBalloon),
         VMSTATE_END_OF_LIST()
     }
 };

@@ -766,7 +766,7 @@ static const VMStateDescription vmstate_virtio_balloon_device = {
         VMSTATE_END_OF_LIST()
     },
     .subsections = (const VMStateDescription * []) {
-        &vmstate_virtio_balloon_free_page_report,
+        &vmstate_virtio_balloon_free_page_hint,
         NULL
     }
 };

@@ -797,12 +797,12 @@ static void virtio_balloon_device_realize(DeviceState *dev, Error **errp)
                            VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
         s->free_page_vq = virtio_add_queue(vdev, VIRTQUEUE_MAX_SIZE,
                                            virtio_balloon_handle_free_page_vq);
-        s->free_page_report_status = FREE_PAGE_REPORT_S_STOP;
-        s->free_page_report_cmd_id =
-                           VIRTIO_BALLOON_FREE_PAGE_REPORT_CMD_ID_MIN;
-        s->free_page_report_notify.notify =
-                                       virtio_balloon_free_page_report_notify;
-        precopy_add_notifier(&s->free_page_report_notify);
+        s->free_page_hint_status = FREE_PAGE_HINT_S_STOP;
+        s->free_page_hint_cmd_id =
+                           VIRTIO_BALLOON_FREE_PAGE_HINT_CMD_ID_MIN;
+        s->free_page_hint_notify.notify =
+                                       virtio_balloon_free_page_hint_notify;
+        precopy_add_notifier(&s->free_page_hint_notify);
         if (s->iothread) {
             object_ref(OBJECT(s->iothread));
             s->free_page_bh = aio_bh_new(iothread_get_aio_context(s->iothread),

@@ -827,7 +827,7 @@ static void virtio_balloon_device_unrealize(DeviceState *dev, Error **errp)
     if (virtio_balloon_free_page_support(s)) {
         qemu_bh_delete(s->free_page_bh);
         virtio_balloon_free_page_stop(s);
-        precopy_remove_notifier(&s->free_page_report_notify);
+        precopy_remove_notifier(&s->free_page_hint_notify);
     }
     balloon_stats_destroy_timer(s);
     qemu_remove_balloon_handler(s);

index d1c968d2376e..108cff97e71a 100644
@@ -23,7 +23,7 @@
 #define VIRTIO_BALLOON(obj) \
         OBJECT_CHECK(VirtIOBalloon, (obj), TYPE_VIRTIO_BALLOON)
 
-#define VIRTIO_BALLOON_FREE_PAGE_REPORT_CMD_ID_MIN 0x80000000
+#define VIRTIO_BALLOON_FREE_PAGE_HINT_CMD_ID_MIN 0x80000000
 
 typedef struct virtio_balloon_stat VirtIOBalloonStat;
 

@@ -33,20 +33,20 @@ typedef struct virtio_balloon_stat_modern {
        uint64_t val;
 } VirtIOBalloonStatModern;
 
-enum virtio_balloon_free_page_report_status {
-    FREE_PAGE_REPORT_S_STOP = 0,
-    FREE_PAGE_REPORT_S_REQUESTED = 1,
-    FREE_PAGE_REPORT_S_START = 2,
-    FREE_PAGE_REPORT_S_DONE = 3,
+enum virtio_balloon_free_page_hint_status {
+    FREE_PAGE_HINT_S_STOP = 0,
+    FREE_PAGE_HINT_S_REQUESTED = 1,
+    FREE_PAGE_HINT_S_START = 2,
+    FREE_PAGE_HINT_S_DONE = 3,
 };
 
 typedef struct VirtIOBalloon {
     VirtIODevice parent_obj;
     VirtQueue *ivq, *dvq, *svq, *free_page_vq;
-    uint32_t free_page_report_status;
+    uint32_t free_page_hint_status;
     uint32_t num_pages;
     uint32_t actual;
-    uint32_t free_page_report_cmd_id;
+    uint32_t free_page_hint_cmd_id;
     uint64_t stats[VIRTIO_BALLOON_S_NR];
     VirtQueueElement *stats_vq_elem;
     size_t stats_vq_offset;

@@ -55,7 +55,7 @@ typedef struct VirtIOBalloon {
     QEMUBH *free_page_bh;
     /*
      * Lock to synchronize threads to access the free page reporting related
-     * fields (e.g. free_page_report_status).
+     * fields (e.g. free_page_hint_status).
      */
     QemuMutex free_page_lock;
     QemuCond  free_page_cond;

@@ -64,7 +64,7 @@ typedef struct VirtIOBalloon {
      * stopped.
      */
     bool block_iothread;
-    NotifierWithReturn free_page_report_notify;
+    NotifierWithReturn free_page_hint_notify;
     int64_t stats_last_update;
     int64_t stats_poll_interval;
     uint32_t host_features;

index a209706b4d8d..1666132a24c1 100644
@@ -634,6 +634,7 @@ static void virtio_balloon_get_config(VirtIODevice *vdev, uint8_t *config_data)
 
     config.num_pages = cpu_to_le32(dev->num_pages);
     config.actual = cpu_to_le32(dev->actual);
+    config.poison_val = cpu_to_le32(dev->poison_val);
 
     if (dev->free_page_hint_status == FREE_PAGE_HINT_S_REQUESTED) {
         config.free_page_hint_cmd_id =

@@ -683,6 +684,14 @@ static ram_addr_t get_current_ram_size(void)
     return size;
 }
 
+static bool virtio_balloon_page_poison_support(void *opaque)
+{
+    VirtIOBalloon *s = opaque;
+    VirtIODevice *vdev = VIRTIO_DEVICE(s);
+
+    return virtio_vdev_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON);
+}
+
 static void virtio_balloon_set_config(VirtIODevice *vdev,
                                       const uint8_t *config_data)
 {

@@ -697,6 +706,10 @@ static void virtio_balloon_set_config(VirtIODevice *vdev,
         qapi_event_send_balloon_change(vm_ram_size -
                         ((ram_addr_t) dev->actual << VIRTIO_BALLOON_PFN_SHIFT));
     }
+    dev->poison_val = 0;
+    if (virtio_balloon_page_poison_support(dev)) {
+        dev->poison_val = le32_to_cpu(config.poison_val);
+    }
     trace_virtio_balloon_set_config(dev->actual, oldactual);
 }
 

@@ -755,6 +768,17 @@ static const VMStateDescription vmstate_virtio_balloon_free_page_hint = {
     }
 };
 
+static const VMStateDescription vmstate_virtio_balloon_page_poison = {
+    .name = "vitio-balloon-device/page-poison",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = virtio_balloon_page_poison_support,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT32(poison_val, VirtIOBalloon),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 static const VMStateDescription vmstate_virtio_balloon_device = {
     .name = "virtio-balloon-device",
     .version_id = 1,

@@ -767,6 +791,7 @@ static const VMStateDescription vmstate_virtio_balloon_device = {
     },
     .subsections = (const VMStateDescription * []) {
         &vmstate_virtio_balloon_free_page_hint,
+        &vmstate_virtio_balloon_page_poison,
         NULL
     }
 };

@@ -854,6 +879,8 @@ static void virtio_balloon_device_reset(VirtIODevice *vdev)
         g_free(s->stats_vq_elem);
         s->stats_vq_elem = NULL;
     }
+
+    s->poison_val = 0;
 }
 
 static void virtio_balloon_set_status(VirtIODevice *vdev, uint8_t status)

@@ -916,6 +943,8 @@ static Property virtio_balloon_properties[] = {
                     VIRTIO_BALLOON_F_DEFLATE_ON_OOM, false),
     DEFINE_PROP_BIT("free-page-hint", VirtIOBalloon, host_features,
                     VIRTIO_BALLOON_F_FREE_PAGE_HINT, false),
+    DEFINE_PROP_BIT("page-poison", VirtIOBalloon, host_features,
+                    VIRTIO_BALLOON_F_PAGE_POISON, true),
     /* QEMU 4.0 accidentally changed the config size even when free-page-hint
      * is disabled, resulting in QEMU 3.1 migration incompatibility.  This
      * property retains this quirk for QEMU 4.1 machine types.

index 108cff97e71a..3ca2a78e1aca 100644
@@ -70,6 +70,7 @@ typedef struct VirtIOBalloon {
     uint32_t host_features;
 
     bool qemu_4_0_config_size;
+    uint32_t poison_val;
 } VirtIOBalloon;
 
 #endif

index 1666132a24c1..53abba290274 100644
@@ -321,6 +321,67 @@ static void balloon_stats_set_poll_interval(Object *obj, Visitor *v,
     balloon_stats_change_timer(s, 0);
 }
 
+static void virtio_balloon_handle_report(VirtIODevice *vdev, VirtQueue *vq)
+{
+    VirtIOBalloon *dev = VIRTIO_BALLOON(vdev);
+    VirtQueueElement *elem;
+
+    while ((elem = virtqueue_pop(vq, sizeof(VirtQueueElement)))) {
+        unsigned int i;
+
+        /*
+         * When we discard the page it has the effect of removing the page
+         * from the hypervisor itself and causing it to be zeroed when it
+         * is returned to us. So we must not discard the page if it is
+         * accessible by another device or process, or if the guest is
+         * expecting it to retain a non-zero value.
+         */
+        if (qemu_balloon_is_inhibited() || dev->poison_val) {
+            goto skip_element;
+        }
+
+        for (i = 0; i < elem->in_num; i++) {
+            void *addr = elem->in_sg[i].iov_base;
+            size_t size = elem->in_sg[i].iov_len;
+            ram_addr_t ram_offset;
+            RAMBlock *rb;
+
+            /*
+             * There is no need to check the memory section to see if
+             * it is ram/readonly/romd like there is for handle_output
+             * below. If the region is not meant to be written to then
+             * address_space_map will have allocated a bounce buffer
+             * and it will be freed in address_space_unmap and trigger
+             * and unassigned_mem_write before failing to copy over the
+             * buffer. If more than one bad descriptor is provided it
+             * will return NULL after the first bounce buffer and fail
+             * to map any resources.
+             */
+            rb = qemu_ram_block_from_host(addr, false, &ram_offset);
+            if (!rb) {
+                trace_virtio_balloon_bad_addr(elem->in_addr[i]);
+                continue;
+            }
+
+            /*
+             * For now we will simply ignore unaligned memory regions, or
+             * regions that overrun the end of the RAMBlock.
+             */
+            if (!QEMU_IS_ALIGNED(ram_offset | size, qemu_ram_pagesize(rb)) ||
+                (ram_offset + size) > qemu_ram_get_used_length(rb)) {
+                continue;
+            }
+
+            ram_block_discard_range(rb, ram_offset, size);
+        }
+
+skip_element:
+        virtqueue_push(vq, elem, 0);
+        virtio_notify(vdev, vq);
+        g_free(elem);
+    }
+}
+
 static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq)
 {
     VirtIOBalloon *s = VIRTIO_BALLOON(vdev);

@@ -841,6 +902,12 @@ static void virtio_balloon_device_realize(DeviceState *dev, Error **errp)
             virtio_error(vdev, "iothread is missing");
         }
     }
+
+    if (virtio_has_feature(s->host_features, VIRTIO_BALLOON_F_REPORTING)) {
+        s->reporting_vq = virtio_add_queue(vdev, 32,
+                                           virtio_balloon_handle_report);
+    }
+
     reset_stats(s);
 }
 

@@ -945,6 +1012,8 @@ static Property virtio_balloon_properties[] = {
                     VIRTIO_BALLOON_F_FREE_PAGE_HINT, false),
     DEFINE_PROP_BIT("page-poison", VirtIOBalloon, host_features,
                     VIRTIO_BALLOON_F_PAGE_POISON, true),
+    DEFINE_PROP_BIT("free-page-reporting", VirtIOBalloon, host_features,
+                    VIRTIO_BALLOON_F_REPORTING, false),
     /* QEMU 4.0 accidentally changed the config size even when free-page-hint
      * is disabled, resulting in QEMU 3.1 migration incompatibility.  This
      * property retains this quirk for QEMU 4.1 machine types.

index 3ca2a78e1aca..28fd2b396087 100644
@@ -42,7 +42,7 @@ enum virtio_balloon_free_page_hint_status {
 
 typedef struct VirtIOBalloon {
     VirtIODevice parent_obj;
-    VirtQueue *ivq, *dvq, *svq, *free_page_vq;
+    VirtQueue *ivq, *dvq, *svq, *free_page_vq, *reporting_vq;
     uint32_t free_page_hint_status;
     uint32_t num_pages;
     uint32_t actual;