virtio-balloon: Implement support for page poison reporting feature

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

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

The value currently has no impact on existing balloon interfaces. In the
case of existing balloon interfaces the onus is on the guest driver to
reapply whatever poison is in place.

When we add free page reporting the poison value is used to determine if
we can perform in-place page reporting. The expectation is that a reported
page will already contain the value specified by the poison, and the
reporting of the page should not change that value.

Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Message-Id: <20200527041400.12700.33251.stgit@localhost.localdomain>

diff --git a/hw/core/machine.c b/hw/core/machine.c
index bb3a7b18b193db5c9c328580000fc0e257744995..9eca7d8c9bfeda14f955dc692f16e1d90b7f76a6 100644 (file)
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -28,7 +28,9 @@
 #include "hw/mem/nvdimm.h"
 #include "migration/vmstate.h"
 
-GlobalProperty hw_compat_5_0[] = {};
+GlobalProperty hw_compat_5_0[] = {
+    { "virtio-balloon-device", "page-poison", "false" },
+};
 const size_t hw_compat_5_0_len = G_N_ELEMENTS(hw_compat_5_0);
 
 GlobalProperty hw_compat_4_2[] = {

diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
index cff8eab6a1526e207305d8db835b7b217cd2eb59..31d3c88482fdce4b828cf86c63edb8fafef99bd1 100644 (file)
--- 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_report_status == FREE_PAGE_REPORT_S_REQUESTED) {
         config.free_page_report_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_report = {
     }
 };
 
+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_report,
+        &vmstate_virtio_balloon_page_poison,
         NULL
     }
 };
@@ -849,6 +874,8 @@ 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.

diff --git a/include/hw/virtio/virtio-balloon.h b/include/hw/virtio/virtio-balloon.h
index d1c968d2376eee7f5567420581c4a9387133ef46..7fe78e5c14d7ea306d3724eeed624fdc17799180 100644 (file)
--- 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