[Qemu-devel] [PATCH v2 for-1.6 0/2] virtio-mmio: fixes to QueueNum, QueueNumMax

[Peter Maydell <peter.maydell@linaro.org>]

These patches fix a couple of bugs in virtio-mmio's
handling of the registers that deal with the queue size:

 * as mst points out, letting the guest flip a queue between
   "exists" and "doesn't exist" is a bad idea
 * QueueNumMax wasn't reading the correct value for nonexistent
   queues

This doesn't include any change to the behaviour of queuesize
on reset (discussed in other thread); the current behaviour is
not a problem for well-behaved guests, and safe in the face
of badly-behaved guests, and currently improving the reset
behaviour is blocked by an unrelated bug.

v1->v2: changes as per mst review:
 * avoid explicit "== 0" comparisons
 * avoid unnecessary parens round comparison ops
 * do the "don't flip between existent and nonexistent" check
   with "!!num != !!oldnum" (and add a comment noting why we're
   doing this check)

Peter Maydell (2):
  hw/virtio/virtio: Don't allow guests to add/remove queues
  hw/virtio/virtio-mmio: Make QueueNumMax read 0 for unavailable queues

 hw/virtio/virtio-mmio.c |    3 +++
 hw/virtio/virtio.c      |   12 +++++++++---
 2 files changed, 12 insertions(+), 3 deletions(-)

-- 
1.7.9.5