[PATCH v21 QEMU 4/5] virtio-balloon: Implement support for page poison tracking feature

[Alexander Duyck <alexander.duyck@gmail.com>]

From: Alexander Duyck <alexander.h.duyck@linux.intel.com>

We need to make certain to advertise support for page poison tracking if
we want to actually get data on if the guest will be poisoning pages.

Add a value for tracking the poison value being used if page poisoning is
enabled. With this we can determine if we will need to skip page reporting
when it is enabled in the future.

Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
---
 hw/virtio/virtio-balloon.c         |    7 +++++++
 include/hw/virtio/virtio-balloon.h |    1 +
 2 files changed, 8 insertions(+)

diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
index a1d6fb52c876..5effc8b4653b 100644
--- a/hw/virtio/virtio-balloon.c
+++ b/hw/virtio/virtio-balloon.c
@@ -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 =
@@ -697,6 +698,10 @@ 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_vdev_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
+        dev->poison_val = le32_to_cpu(config.poison_val);
+    }
     trace_virtio_balloon_set_config(dev->actual, oldactual);
 }
 
@@ -854,6 +859,8 @@ 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)
diff --git a/include/hw/virtio/virtio-balloon.h b/include/hw/virtio/virtio-balloon.h
index 108cff97e71a..3ca2a78e1aca 100644
--- a/include/hw/virtio/virtio-balloon.h
+++ b/include/hw/virtio/virtio-balloon.h
@@ -70,6 +70,7 @@ typedef struct VirtIOBalloon {
     uint32_t host_features;
 
     bool qemu_4_0_config_size;
+    uint32_t poison_val;
 } VirtIOBalloon;
 
 #endif