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Re: [Qemu-devel] [PATCH] virtio-balloon: Fix ballooning not working corr


From: zhanghailiang
Subject: Re: [Qemu-devel] [PATCH] virtio-balloon: Fix ballooning not working correctly when hotplug memory
Date: Thu, 18 Sep 2014 09:47:42 +0800
User-agent: Mozilla/5.0 (Windows NT 6.1; rv:31.0) Gecko/20100101 Thunderbird/31.1.1

Hi,

Ping...

Is anyone concerned about this patch? Is this a bug?

Thanks,
zhanghailiang

On 2014/9/15 20:29, zhanghailiang wrote:
When do memory balloon, it references the ram_size as the real ram size of VM,
But here ram_size is not include the hotplugged memory, and the result will
be confused.

Steps to reproduce:
(1)Start VM: qemu -m size=1024,slots=4,maxmem=8G
(2)In VM: #free -m : 1024M
(3)qmp balloon 512M
(4)In VM: #free -m : 512M
(5)hotplug pc-dimm 1G
(6)In VM: #free -m : 1512M
(7)qmp balloon 256M
(8)In VM: #free -m :1256M

Here we add a new global variable 'vm_ram_size', it will stat
the VM's real ram size which include configured ram and hotplugged ram.
virtio-balloon will reference this parameter.

Signed-off-by: zhanghailiang <address@hidden>
---
  hw/i386/pc.c               |  1 +
  hw/virtio/virtio-balloon.c | 10 +++++-----
  include/exec/cpu-common.h  |  1 +
  vl.c                       |  3 +++
  4 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index b6c9b61..817810b 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -1606,6 +1606,7 @@ static void pc_dimm_plug(HotplugHandler *hotplug_dev,
      memory_region_add_subregion(&pcms->hotplug_memory,
                                  addr - pcms->hotplug_memory_base, mr);
      vmstate_register_ram(mr, dev);
+    vm_ram_size += memory_region_size(mr);

      hhc = HOTPLUG_HANDLER_GET_CLASS(pcms->acpi_dev);
      hhc->plug(HOTPLUG_HANDLER(pcms->acpi_dev), dev, &local_err);
diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
index 2c30b3d..205e1fe 100644
--- a/hw/virtio/virtio-balloon.c
+++ b/hw/virtio/virtio-balloon.c
@@ -292,7 +292,7 @@ static void virtio_balloon_set_config(VirtIODevice *vdev,
      memcpy(&config, config_data, sizeof(struct virtio_balloon_config));
      dev->actual = le32_to_cpu(config.actual);
      if (dev->actual != oldactual) {
-        qapi_event_send_balloon_change(ram_size -
+        qapi_event_send_balloon_change(vm_ram_size -
                          ((ram_addr_t) dev->actual << 
VIRTIO_BALLOON_PFN_SHIFT),
                          &error_abort);
      }
@@ -307,7 +307,7 @@ static uint32_t virtio_balloon_get_features(VirtIODevice 
*vdev, uint32_t f)
  static void virtio_balloon_stat(void *opaque, BalloonInfo *info)
  {
      VirtIOBalloon *dev = opaque;
-    info->actual = ram_size - ((uint64_t) dev->actual <<
+    info->actual = vm_ram_size - ((uint64_t) dev->actual <<
                                 VIRTIO_BALLOON_PFN_SHIFT);
  }

@@ -316,11 +316,11 @@ static void virtio_balloon_to_target(void *opaque, 
ram_addr_t target)
      VirtIOBalloon *dev = VIRTIO_BALLOON(opaque);
      VirtIODevice *vdev = VIRTIO_DEVICE(dev);

-    if (target > ram_size) {
-        target = ram_size;
+    if (target > vm_ram_size) {
+        target = vm_ram_size;
      }
      if (target) {
-        dev->num_pages = (ram_size - target) >> VIRTIO_BALLOON_PFN_SHIFT;
+        dev->num_pages = (vm_ram_size - target) >> VIRTIO_BALLOON_PFN_SHIFT;
          virtio_notify_config(vdev);
      }
  }
diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
index e3ec4c8..f55db6a 100644
--- a/include/exec/cpu-common.h
+++ b/include/exec/cpu-common.h
@@ -46,6 +46,7 @@ typedef uintptr_t ram_addr_t;
  #endif

  extern ram_addr_t ram_size;
+extern ram_addr_t vm_ram_size;

  /* memory API */

diff --git a/vl.c b/vl.c
index 9c9acf5..5d20d0c 100644
--- a/vl.c
+++ b/vl.c
@@ -132,6 +132,7 @@ DisplayType display_type = DT_DEFAULT;
  static int display_remote;
  const char* keyboard_layout = NULL;
  ram_addr_t ram_size;
+ram_addr_t vm_ram_size; /* ram_size + hotplugged ram size */
  const char *mem_path = NULL;
  int mem_prealloc = 0; /* force preallocation of physical target memory */
  int nb_nics;
@@ -3015,6 +3016,7 @@ int main(int argc, char **argv, char **envp)
      machine_class = find_default_machine();
      cpu_model = NULL;
      ram_size = default_ram_size;
+    vm_ram_size = ram_size;
      snapshot = 0;
      cyls = heads = secs = 0;
      translation = BIOS_ATA_TRANSLATION_AUTO;
@@ -3388,6 +3390,7 @@ int main(int argc, char **argv, char **envp)
                              "'%s' option\n", slots_str ? "maxmem" : "slots");
                      exit(EXIT_FAILURE);
                  }
+                vm_ram_size = ram_size;
                  break;
              }
  #ifdef CONFIG_TPM






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