Re: [PATCH v2] virtio-balloon: always indicate S_DONE when migration fails

[David Hildenbrand]

On 22.07.20 14:04, Michael S. Tsirkin wrote:
> On Mon, Jun 29, 2020 at 10:06:15AM +0200, David Hildenbrand wrote:
>> If something goes wrong during precopy, before stopping the VM, we will
>> never send a S_DONE indication to the VM, resulting in the hinted pages
>> not getting released to be used by the guest OS (e.g., Linux).
>>
>> Easy to reproduce:
>> 1. Start migration (e.g., HMP "migrate -d 'exec:gzip -c > STATEFILE.gz'")
>> 2. Cancel migration (e.g., HMP "migrate_cancel")
>> 3. Oberve in the guest (e.g., cat /proc/meminfo) that there is basically
>>    no free memory left.
>>
>> While at it, add similar locking to virtio_balloon_free_page_done() as
>> done in virtio_balloon_free_page_stop. Locking is still weird, but that
>> has to be sorted out separately.
>>
>> There is nothing to do in the PRECOPY_NOTIFY_COMPLETE case. Add some
>> comments regarding S_DONE handling.
>>
>> Fixes: c13c4153f76d ("virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT")
>> Reviewed-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
>> Cc: Wei Wang <wei.w.wang@intel.com>
>> Cc: Alexander Duyck <alexander.duyck@gmail.com>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
> 
> IIUC this is superceded by Alexander's patches right?

Not that I know ... @Alex?

> If not pls rebase ...
> 



-- 
Thanks,

David / dhildenb