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

[Michael S. Tsirkin]

On Wed, Jul 22, 2020 at 02:05:19PM +0200, David Hildenbrand wrote:
> 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 IIUC this is superceded by Alexander's patches right?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 ...
> > 

OK then I guess I was confused. This is older so I guess I should
have applied this and asked Alex to rebase his patches, but I did the
reverse.., Sorry about that. Could you rebase on top of
the pci tree pls?


Thanks and sorry for messing up.

> 
> 
> -- 
> Thanks,
> 
> David / dhildenb