Re: [PATCH v1 16/17] virtio-mem: Allow notifiers for size changes

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* David Hildenbrand (david@redhat.com) wrote:
> We want to send qapi events in case the size of a virtio-mem device
> changes. This allows upper layers to always know how much memory is
> actually currently consumed via a virtio-mem device.
> 
> Unfortuantely, we have to report the id of our proxy device. Let's provide
> an easy way for our proxy device to register, so it can send the qapi
> events. Piggy-backing on the notifier infrastructure (although we'll
> only ever have one notifier registered) seems to be an easy way.
> 
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> Cc: Igor Mammedov <imammedo@redhat.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  hw/virtio/virtio-mem.c         | 21 ++++++++++++++++++++-
>  include/hw/virtio/virtio-mem.h |  5 +++++
>  2 files changed, 25 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c
> index e25b2c74f2..88a99a0d90 100644
> --- a/hw/virtio/virtio-mem.c
> +++ b/hw/virtio/virtio-mem.c
> @@ -198,6 +198,7 @@ static int virtio_mem_state_change_request(VirtIOMEM *vmem, uint64_t gpa,
>      } else {
>          vmem->size -= size;
>      }
> +    notifier_list_notify(&vmem->size_change_notifiers, &vmem->size);
>      return VIRTIO_MEM_RESP_ACK;
>  }
>  
> @@ -253,7 +254,10 @@ static int virtio_mem_unplug_all(VirtIOMEM *vmem)
>          return -EBUSY;
>      }
>      bitmap_clear(vmem->bitmap, 0, vmem->bitmap_size);
> -    vmem->size = 0;
> +    if (vmem->size != 0) {
> +        vmem->size = 0;
> +        notifier_list_notify(&vmem->size_change_notifiers, &vmem->size);
> +    }
>  
>      virtio_mem_resize_usable_region(vmem, vmem->requested_size, true);
>      return 0;
> @@ -594,6 +598,18 @@ static MemoryRegion *virtio_mem_get_memory_region(VirtIOMEM *vmem, Error **errp)
>      return &vmem->memdev->mr;
>  }
>  
> +static void virtio_mem_add_size_change_notifier(VirtIOMEM *vmem,
> +                                                Notifier *notifier)
> +{
> +    notifier_list_add(&vmem->size_change_notifiers, notifier);
> +}
> +
> +static void virtio_mem_remove_size_change_notifier(VirtIOMEM *vmem,
> +                                                   Notifier *notifier)
> +{
> +    notifier_remove(notifier);
> +}
> +
>  static void virtio_mem_get_size(Object *obj, Visitor *v, const char *name,
>                                  void *opaque, Error **errp)
>  {
> @@ -705,6 +721,7 @@ static void virtio_mem_instance_init(Object *obj)
>      VirtIOMEM *vmem = VIRTIO_MEM(obj);
>  
>      vmem->block_size = VIRTIO_MEM_MIN_BLOCK_SIZE;
> +    notifier_list_init(&vmem->size_change_notifiers);
>  
>      object_property_add(obj, VIRTIO_MEM_SIZE_PROP, "size", virtio_mem_get_size,
>                          NULL, NULL, NULL, &error_abort);
> @@ -743,6 +760,8 @@ static void virtio_mem_class_init(ObjectClass *klass, void *data)
>  
>      vmc->fill_device_info = virtio_mem_fill_device_info;
>      vmc->get_memory_region = virtio_mem_get_memory_region;
> +    vmc->add_size_change_notifier = virtio_mem_add_size_change_notifier;
> +    vmc->remove_size_change_notifier = virtio_mem_remove_size_change_notifier;
>  }
>  
>  static const TypeInfo virtio_mem_info = {
> diff --git a/include/hw/virtio/virtio-mem.h b/include/hw/virtio/virtio-mem.h
> index 27158cb611..5820b5c23e 100644
> --- a/include/hw/virtio/virtio-mem.h
> +++ b/include/hw/virtio/virtio-mem.h
> @@ -66,6 +66,9 @@ typedef struct VirtIOMEM {
>      /* block size and alignment */
>      uint32_t block_size;
>      uint32_t migration_block_size;
> +
> +    /* notifiers to notify when "size" changes */
> +    NotifierList size_change_notifiers;
>  } VirtIOMEM;
>  
>  typedef struct VirtIOMEMClass {
> @@ -75,6 +78,8 @@ typedef struct VirtIOMEMClass {
>      /* public */
>      void (*fill_device_info)(const VirtIOMEM *vmen, VirtioMEMDeviceInfo *vi);
>      MemoryRegion *(*get_memory_region)(VirtIOMEM *vmem, Error **errp);
> +    void (*add_size_change_notifier)(VirtIOMEM *vmem, Notifier *notifier);
> +    void (*remove_size_change_notifier)(VirtIOMEM *vmem, Notifier *notifier);
>  } VirtIOMEMClass;
>  
>  #endif
> -- 
> 2.25.3
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK