Let the host effectively inflate the balloon in access/contiguity-aware
way when the guest kernel is compiled with specific kernel config. When
the config is enabled and the host requests balloon size change,
virtio-balloon adjusts ACMA's max-mem parameter instead of allocating
guest pages and put it into the balloon. As a result, the host can use
the requested amount of guest memory, so from the host's perspective,
the ballooning just works, but in transparent and
access/contiguity-aware way.
Signed-off-by: SeongJae Park <sj@xxxxxxxxxx>
---
drivers/virtio/virtio_balloon.c | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 1f5b3dd31fcf..a954d75789ae 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -472,6 +472,32 @@ static void virtballoon_changed(struct virtio_device *vdev)
struct virtio_balloon *vb = vdev->priv;
unsigned long flags;
+#ifdef CONFIG_ACMA_BALLOON
+ s64 target;
+ u32 num_pages;
+
+
+ /* Legacy balloon config space is LE, unlike all other devices. */
+ virtio_cread_le(vb->vdev, struct virtio_balloon_config, num_pages,
+ &num_pages);
+
+ /*
+ * Aligned up to guest page size to avoid inflating and deflating
+ * balloon endlessly.
+ */
+ target = ALIGN(num_pages, VIRTIO_BALLOON_PAGES_PER_PAGE);
+
+ /*
+ * If the given new max mem size is larger than current acma's max mem
+ * size, same to normal max mem adjustment.
+ * If the given new max mem size is smaller than current acma's max mem
+ * size, strong aggressiveness is applied while memory for meeting the
+ * new max mem is met is stolen.
+ */
+ acma_set_max_mem_aggressive(totalram_pages() - target);
+ return;
+#endif
+
spin_lock_irqsave(&vb->stop_update_lock, flags);
if (!vb->stop_update) {
start_update_balloon_size(vb);
--
2.39.2
