qemu-e2k/hw/virtio
Dr. David Alan Gilbert 371ff5a3f0 Inhibit ballooning during postcopy
Postcopy detects accesses to pages that haven't been transferred yet
using userfaultfd, and it causes exceptions on pages that are 'not
present'.
Ballooning also causes pages to be marked as 'not present' when the
guest inflates the balloon.
Potentially a balloon could be inflated to discard pages that are
currently inflight during postcopy and that may be arriving at about
the same time.

To avoid this confusion, disable ballooning during postcopy.

When disabled we drop balloon requests from the guest.  Since ballooning
is generally initiated by the host, the management system should avoid
initiating any balloon instructions to the guest during migration,
although it's not possible to know how long it would take a guest to
process a request made prior to the start of migration.
Guest initiated ballooning will not know if it's really freed a page
of host memory or not.

Queueing the requests until after migration would be nice, but is
non-trivial, since the set of inflate/deflate requests have to
be compared with the state of the page to know what the final
outcome is allowed to be.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
2015-11-10 15:00:28 +01:00
..
dataplane dataplane: support non-contigious s/g 2015-11-09 09:59:32 +00:00
Makefile.objs dataplane: endianness-aware accesses 2015-02-16 15:07:16 +00:00
vhost-backend.c vhost: use a function for each call 2015-10-22 14:34:49 +03:00
vhost-user.c vhost-user: cleanup msg size math 2015-10-29 11:05:24 +02:00
vhost.c vhost: set the correct queue index in case of migration with multiqueue 2015-10-22 14:34:50 +03:00
virtio-balloon.c Inhibit ballooning during postcopy 2015-11-10 15:00:28 +01:00
virtio-bus.c virtio: get_features() can fail 2015-07-27 18:11:53 +03:00
virtio-mmio.c virtio: allow virtio-1 queue layout 2015-06-10 18:15:04 +02:00
virtio-pci.c kvm: Pass PCI device pointer to MSI routing functions 2015-10-19 10:13:07 +02:00
virtio-pci.h virtio-input: Fix device introspection on non-Linux hosts 2015-10-09 15:25:56 +02:00
virtio-rng.c virtio: get_features() can fail 2015-07-27 18:11:53 +03:00
virtio.c virtio: drop virtqueue_map_sg 2015-10-29 11:05:24 +02:00