On 23.01.20 15:08, Julia Suvorova wrote:
> On Thu, Jan 16, 2020 at 1:36 PM David Hildenbrand <da...@redhat.com> wrote:
>>
>> On 15.01.20 23:40, Julia Suvorova wrote:
>>> Hot-unplug takes some time due to communication with the guest.
>>> Do not change the device while freeing up resources.
>>>
>>> Signed-off-by: Julia Suvorova <jus...@redhat.com>
>>> ---
>>> balloon.c | 2 +-
>>> hw/virtio/virtio-balloon.c | 9 ++++++++-
>>> include/sysemu/balloon.h | 2 +-
>>> 3 files changed, 10 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/balloon.c b/balloon.c
>>> index f104b42961..998ec53a0f 100644
>>> --- a/balloon.c
>>> +++ b/balloon.c
>>> @@ -119,5 +119,5 @@ void qmp_balloon(int64_t target, Error **errp)
>>> }
>>>
>>> trace_balloon_event(balloon_opaque, target);
>>> - balloon_event_fn(balloon_opaque, target);
>>> + balloon_event_fn(balloon_opaque, target, errp);
>>> }
>>> diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
>>> index 57f3b9f22d..0fa4e4454b 100644
>>> --- a/hw/virtio/virtio-balloon.c
>>> +++ b/hw/virtio/virtio-balloon.c
>>> @@ -717,12 +717,19 @@ static void virtio_balloon_stat(void *opaque,
>>> BalloonInfo *info)
>>> VIRTIO_BALLOON_PFN_SHIFT);
>>> }
>>>
>>> -static void virtio_balloon_to_target(void *opaque, ram_addr_t target)
>>> +static void virtio_balloon_to_target(void *opaque, ram_addr_t target,
>>> + Error **errp)
>>> {
>>> + DeviceState *bus_dev = qdev_get_bus_device(DEVICE(opaque));
>>> VirtIOBalloon *dev = VIRTIO_BALLOON(opaque);
>>> VirtIODevice *vdev = VIRTIO_DEVICE(dev);
>>> ram_addr_t vm_ram_size = get_current_ram_size();
>>>
>>> + if (bus_dev && bus_dev->pending_deleted_event) {
>>> + error_setg(errp, "Hot-unplug of %s is in progress", vdev->name);
>>> + return;
>>> + }
>>> +
>>
>> How exactly does this help? The guest is free to inflate/deflate
>> whenever it wants.
>
> Guest is aware of hot-unplug start, and virtio driver should not
> initiate any operations. This patch just restricts issuing commands
> from qmp monitor.
Why shouldn't the guest driver inflate/deflate while memory hotplug is
going on?
Simple balloon compaction in a Linux guest -> deflate/inflate triggered
in the hypervisor.
--
Thanks,
David / dhildenb
