[Qemu-devel] [PATCH v3 0/2] balloon: add a feature bit to let Guest OS deflate virtio_balloon on OOM

[Qemu-devel] [PATCH v3 0/2] balloon: add a feature bit to let Guest OS deflate virtio_balloon on OOM

[Denis V. Lunev]

Excessive virtio_balloon inflation can cause invocation of OOM-killer,
when Linux is under severe memory pressure. Various mechanisms are
responsible for correct virtio_balloon memory management. Nevertheless it
is often the case that these control tools does not have enough time to
react on fast changing memory load. As a result OS runs out of memory and
invokes OOM-killer. The balancing of memory by use of the virtio balloon
should not cause the termination of processes while there are pages in the
balloon. Now there is no way for virtio balloon driver to free memory at
the last moment before some process get killed by OOM-killer.

This does not provide a security breach as balloon itself is running
inside Guest OS and is working in the cooperation with the host. Thus
some improvements from Guest side should be considered as normal.

To solve the problem, introduce a virtio_balloon callback which is
expected to be called from the oom notifier call chain in out_of_memory()
function. If virtio balloon could release some memory, it will make the
system to return and retry the allocation that forced the out of memory
killer to run.

This behavior should be enabled if and only if appropriate feature bit
is set on the device. It is off by default.

This functionality was recently merged into vanilla Linux (actually in
linux-next at the moment)

  commit 5a10b7dbf904bfe01bb9fcc6298f7df09eed77d5
  Author: Raushaniya Maksudova <rmaksudova@parallels.com>
  Date:   Mon Nov 10 09:36:29 2014 +1030

This patch adds respective control bits into QEMU. It introduces
deflate-on-oom option for baloon device which do the trick.

Changes from v2:
- fixed mistake with bit number in virtio_balloon_get_features

Changes from v1:
- From: in patch 1 according to the original ownership
- feature processing in patch 2 as suggested by Michael. It could be done
  without additional field, but this will require to move the property
  level up, i.e. to PCI & CCW level.

Signed-off-by: Raushaniya Maksudova <rmaksudova@parallels.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Anthony Liguori <aliguori@amazon.com>
CC: Michael S. Tsirkin <mst@redhat.com>

[Qemu-devel] [PATCH 1/2] balloon: call qdev_alias_all_properties for proxy dev in balloon class init

[Denis V. Lunev]

The idea is that all other virtio devices are calling this helper
to merge properties of the proxy device. This is the only difference
in between this helper and code in inside virtio_instance_init_common.
The patch should not cause any harm as property list in generic balloon
code is empty.

This also allows to avoid some dummy errors like fixed by this
    commit 91ba21208839643603e7f7fa5864723c3f371ebe
    Author: Gonglei <arei.gonglei@huawei.com>
    Date:   Tue Sep 30 14:10:35 2014 +0800
    virtio-balloon: fix virtio-balloon child refcount in transports

Signed-off-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: Raushaniya Maksudova <rmaksudova@parallels.com>
Revieved-by: Cornelia Huck <cornelia.huck@de.ibm.com>
CC: Christian Borntraeger <borntraeger@de.ibm.com>
CC: Anthony Liguori <aliguori@amazon.com>
CC: Michael S. Tsirkin <mst@redhat.com>
---
 hw/s390x/virtio-ccw.c  | 5 ++---
 hw/virtio/virtio-pci.c | 5 ++---
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/hw/s390x/virtio-ccw.c b/hw/s390x/virtio-ccw.c
index ea236c9..82da894 100644
--- a/hw/s390x/virtio-ccw.c
+++ b/hw/s390x/virtio-ccw.c
@@ -899,9 +899,8 @@ static void balloon_ccw_stats_set_poll_interval(Object *obj, struct Visitor *v,
 static void virtio_ccw_balloon_instance_init(Object *obj)
 {
     VirtIOBalloonCcw *dev = VIRTIO_BALLOON_CCW(obj);
-    object_initialize(&dev->vdev, sizeof(dev->vdev), TYPE_VIRTIO_BALLOON);
-    object_property_add_child(obj, "virtio-backend", OBJECT(&dev->vdev), NULL);
-    object_unref(OBJECT(&dev->vdev));
+    virtio_instance_init_common(obj, &dev->vdev, sizeof(dev->vdev),
+                                TYPE_VIRTIO_BALLOON);
     object_property_add(obj, "guest-stats", "guest statistics",
                         balloon_ccw_stats_get_all, NULL, NULL, dev, NULL);
 
diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index dde1d73..745324b 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -1316,9 +1316,8 @@ static void virtio_balloon_pci_class_init(ObjectClass *klass, void *data)
 static void virtio_balloon_pci_instance_init(Object *obj)
 {
     VirtIOBalloonPCI *dev = VIRTIO_BALLOON_PCI(obj);
-    object_initialize(&dev->vdev, sizeof(dev->vdev), TYPE_VIRTIO_BALLOON);
-    object_property_add_child(obj, "virtio-backend", OBJECT(&dev->vdev), NULL);
-    object_unref(OBJECT(&dev->vdev));
+    virtio_instance_init_common(obj, &dev->vdev, sizeof(dev->vdev),
+                                TYPE_VIRTIO_BALLOON);
     object_property_add(obj, "guest-stats", "guest statistics",
                         balloon_pci_stats_get_all, NULL, NULL, dev,
                         NULL);
-- 
1.9.1

[Qemu-devel] [PATCH 2/2] balloon: add a feature bit to let Guest OS deflate balloon on oom

[Denis V. Lunev]

Excessive virtio_balloon inflation can cause invocation of OOM-killer,
when Linux is under severe memory pressure. Various mechanisms are
responsible for correct virtio_balloon memory management. Nevertheless it
is often the case that these control tools does not have enough time to
react on fast changing memory load. As a result OS runs out of memory and
invokes OOM-killer. The balancing of memory by use of the virtio balloon
should not cause the termination of processes while there are pages in the
balloon. Now there is no way for virtio balloon driver to free memory at
the last moment before some process get killed by OOM-killer.

This does not provide a security breach as balloon itself is running
inside Guest OS and is working in the cooperation with the host. Thus
some improvements from Guest side should be considered as normal.

To solve the problem, introduce a virtio_balloon callback which is
expected to be called from the oom notifier call chain in out_of_memory()
function. If virtio balloon could release some memory, it will make the
system to return and retry the allocation that forced the out of memory
killer to run.

This behavior should be enabled if and only if appropriate feature bit
is set on the device. It is off by default.

This functionality was recently merged into vanilla Linux (actually in
linux-next at the moment)

  commit 5a10b7dbf904bfe01bb9fcc6298f7df09eed77d5
  Author: Raushaniya Maksudova <rmaksudova@parallels.com>
  Date:   Mon Nov 10 09:36:29 2014 +1030

This patch adds respective control bits into QEMU. It introduces
deflate-on-oom option for baloon device which do the trick.

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Raushaniya Maksudova <rmaksudova@parallels.com>
CC: Anthony Liguori <aliguori@amazon.com>
CC: Michael S. Tsirkin <mst@redhat.com>
---
 hw/virtio/virtio-balloon.c         | 6 ++++--
 include/hw/virtio/virtio-balloon.h | 2 ++
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
index 7bfbb75..a54d026 100644
--- a/hw/virtio/virtio-balloon.c
+++ b/hw/virtio/virtio-balloon.c
@@ -305,8 +305,8 @@ static void virtio_balloon_set_config(VirtIODevice *vdev,
 
 static uint32_t virtio_balloon_get_features(VirtIODevice *vdev, uint32_t f)
 {
-    f |= (1 << VIRTIO_BALLOON_F_STATS_VQ);
-    return f;
+    VirtIOBalloon *dev = VIRTIO_BALLOON(vdev);
+    return f | (1u << VIRTIO_BALLOON_F_STATS_VQ) | dev->host_features;
 }
 
 static void virtio_balloon_stat(void *opaque, BalloonInfo *info)
@@ -409,6 +409,8 @@ static void virtio_balloon_device_unrealize(DeviceState *dev, Error **errp)
 }
 
 static Property virtio_balloon_properties[] = {
+    DEFINE_PROP_BIT("deflate-on-oom", VirtIOBalloon, host_features,
+                    VIRTIO_BALLOON_F_DEFLATE_ON_OOM, false),
     DEFINE_PROP_END_OF_LIST(),
 };
 
diff --git a/include/hw/virtio/virtio-balloon.h b/include/hw/virtio/virtio-balloon.h
index f863bfe..2e1ccd9 100644
--- a/include/hw/virtio/virtio-balloon.h
+++ b/include/hw/virtio/virtio-balloon.h
@@ -30,6 +30,7 @@
 /* The feature bitmap for virtio balloon */
 #define VIRTIO_BALLOON_F_MUST_TELL_HOST 0 /* Tell before reclaiming pages */
 #define VIRTIO_BALLOON_F_STATS_VQ 1       /* Memory stats virtqueue */
+#define VIRTIO_BALLOON_F_DEFLATE_ON_OOM 2 /* Deflate balloon on OOM */
 
 /* Size of a PFN in the balloon interface. */
 #define VIRTIO_BALLOON_PFN_SHIFT 12
@@ -67,6 +68,7 @@ typedef struct VirtIOBalloon {
     QEMUTimer *stats_timer;
     int64_t stats_last_update;
     int64_t stats_poll_interval;
+    uint32_t host_features;
 } VirtIOBalloon;
 
 #endif
-- 
1.9.1

Re: [Qemu-devel] [PATCH v3 0/2] balloon: add a feature bit to let Guest OS deflate virtio_balloon on OOM

[Denis V. Lunev]

On 27/11/14 15:44, Denis V. Lunev wrote:
> Excessive virtio_balloon inflation can cause invocation of OOM-killer,
> when Linux is under severe memory pressure. Various mechanisms are
> responsible for correct virtio_balloon memory management. Nevertheless it
> is often the case that these control tools does not have enough time to
> react on fast changing memory load. As a result OS runs out of memory and
> invokes OOM-killer. The balancing of memory by use of the virtio balloon
> should not cause the termination of processes while there are pages in the
> balloon. Now there is no way for virtio balloon driver to free memory at
> the last moment before some process get killed by OOM-killer.
>
> This does not provide a security breach as balloon itself is running
> inside Guest OS and is working in the cooperation with the host. Thus
> some improvements from Guest side should be considered as normal.
>
> To solve the problem, introduce a virtio_balloon callback which is
> expected to be called from the oom notifier call chain in out_of_memory()
> function. If virtio balloon could release some memory, it will make the
> system to return and retry the allocation that forced the out of memory
> killer to run.
>
> This behavior should be enabled if and only if appropriate feature bit
> is set on the device. It is off by default.
>
> This functionality was recently merged into vanilla Linux (actually in
> linux-next at the moment)
>
>    commit 5a10b7dbf904bfe01bb9fcc6298f7df09eed77d5
>    Author: Raushaniya Maksudova <rmaksudova@parallels.com>
>    Date:   Mon Nov 10 09:36:29 2014 +1030
>
> This patch adds respective control bits into QEMU. It introduces
> deflate-on-oom option for baloon device which do the trick.
>
> Changes from v2:
> - fixed mistake with bit number in virtio_balloon_get_features
>
> Changes from v1:
> - From: in patch 1 according to the original ownership
> - feature processing in patch 2 as suggested by Michael. It could be done
>    without additional field, but this will require to move the property
>    level up, i.e. to PCI & CCW level.
>
> Signed-off-by: Raushaniya Maksudova <rmaksudova@parallels.com>
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Anthony Liguori <aliguori@amazon.com>
> CC: Michael S. Tsirkin <mst@redhat.com>
>
ping

Re: [Qemu-devel] [PATCH v3 0/2] balloon: add a feature bit to let Guest OS deflate virtio_balloon on OOM

[Denis V. Lunev]

On 15/12/14 13:03, Denis V. Lunev wrote:
> On 27/11/14 15:44, Denis V. Lunev wrote:
>> Excessive virtio_balloon inflation can cause invocation of OOM-killer,
>> when Linux is under severe memory pressure. Various mechanisms are
>> responsible for correct virtio_balloon memory management. 
>> Nevertheless it
>> is often the case that these control tools does not have enough time to
>> react on fast changing memory load. As a result OS runs out of memory 
>> and
>> invokes OOM-killer. The balancing of memory by use of the virtio balloon
>> should not cause the termination of processes while there are pages 
>> in the
>> balloon. Now there is no way for virtio balloon driver to free memory at
>> the last moment before some process get killed by OOM-killer.
>>
>> This does not provide a security breach as balloon itself is running
>> inside Guest OS and is working in the cooperation with the host. Thus
>> some improvements from Guest side should be considered as normal.
>>
>> To solve the problem, introduce a virtio_balloon callback which is
>> expected to be called from the oom notifier call chain in 
>> out_of_memory()
>> function. If virtio balloon could release some memory, it will make the
>> system to return and retry the allocation that forced the out of memory
>> killer to run.
>>
>> This behavior should be enabled if and only if appropriate feature bit
>> is set on the device. It is off by default.
>>
>> This functionality was recently merged into vanilla Linux (actually in
>> linux-next at the moment)
>>
>>    commit 5a10b7dbf904bfe01bb9fcc6298f7df09eed77d5
>>    Author: Raushaniya Maksudova <rmaksudova@parallels.com>
>>    Date:   Mon Nov 10 09:36:29 2014 +1030
>>
>> This patch adds respective control bits into QEMU. It introduces
>> deflate-on-oom option for baloon device which do the trick.
>>
>> Changes from v2:
>> - fixed mistake with bit number in virtio_balloon_get_features
>>
>> Changes from v1:
>> - From: in patch 1 according to the original ownership
>> - feature processing in patch 2 as suggested by Michael. It could be 
>> done
>>    without additional field, but this will require to move the property
>>    level up, i.e. to PCI & CCW level.
>>
>> Signed-off-by: Raushaniya Maksudova <rmaksudova@parallels.com>
>> Signed-off-by: Denis V. Lunev <den@openvz.org>
>> CC: Anthony Liguori <aliguori@amazon.com>
>> CC: Michael S. Tsirkin <mst@redhat.com>
>>
> ping
ping. Corresponding changes have been just merged into vanilla Linux.