virtio_balloon: disable indirect descriptors

Browse source

The page reporting callback submits an sg list to the reporting
virtqueue.  With VIRTIO_RING_F_INDIRECT_DESC negotiated and
total_sg > 1 (which it typically is), virtqueue_add reports it to the
host by allocating an indirect descriptor via kmalloc(GFP_KERNEL).

This is not pretty: the reporting worker isolates potentially hundreds
of MB of free pages from the buddy allocator (reported pages are at
least pageblock_order, and the sg can contain up to
PAGE_REPORTING_CAPACITY entries of varying orders).  As the result,
very theoretically, the kmalloc might trigger OOM when we have in fact a
ton of free memory.

Clear VIRTIO_RING_F_INDIRECT_DESC, to avoid using indirect descriptors.

Fixes: b0c504f154 ("virtio-balloon: add support for providing free page reports to host")
Assisted-by: Claude:claude-opus-4-6
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <73fac8a629fd9aca7bb3265ac243a769c28af25d.1783232420.git.mst@redhat.com>

...

This commit is contained in:

Michael S. Tsirkin 2026-07-05 02:24:18 -04:00

parent fa8833c085

commit 281eb4732a

1 changed files with 6 additions and 0 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

6

drivers/virtio/virtio_balloon.c

View file