On 05.12.19 11:08, Igor Mammedov wrote:
On Wed, 4 Dec 2019 21:48:07 +0100 David Hildenbrand david@redhat.com wrote:
In case we have to migrate a ballon page to a newpage of another zone, the managed page count of both zones is wrong. Paired with memory offlining (which will adjust the managed page count), we can trigger kernel crashes and all kinds of different symptoms.
One way to reproduce:
- Start a QEMU guest with 4GB, no NUMA
- Hotplug a 1GB DIMM and only the memory to ZONE_NORMAL
^^^^should it be "online" ?
Very right! [...]
mutex_unlock(&vb->balloon_lock);
- /* fixup the managed page count (esp. of the zone) */
- if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
what happens when balloon has the feature?
With that feature we don't touch the managed page counts at all (see the other 2 adjust_managed_page_count() callers in this file).
adjust_managed_page_count(page, 1);adjust_managed_page_count(newpage, -1);- }
- put_page(page); /* balloon reference */
return MIGRATEPAGE_SUCCESS;
BTW, I posted a v2 just some minutes ago (https://lkml.kernel.org/r/20191205092420.6934-1-david@redhat.com)
Thanks!