Merge remote-tracking branch 'remotes/jasowang/tags/net-pull-request' into staging

Want to send earlier but most patches just come.

- fix vhost-vdpa issues when no peer
- fix virtio-pci queue enabling index value
- forbid reentrant RX

Changes from V1:

- drop the patch that has been merged

# gpg: Signature made Tue 28 Jul 2020 09:59:41 BST
# gpg:                using RSA key EF04965B398D6211
# gpg: Good signature from "Jason Wang (Jason Wang on RedHat) <[email protected]>" [marginal]
# gpg: WARNING: This key is not certified with sufficiently trusted signatures!
# gpg:          It is not certain that the signature belongs to the owner.
# Primary key fingerprint: 215D 46F4 8246 689E C77F  3562 EF04 965B 398D 6211

* remotes/jasowang/tags/net-pull-request:
  net: forbid the reentrant RX
  virtio-net: check the existence of peer before accessing vDPA config
  virtio-pci: fix wrong index in virtio_pci_queue_enabled

Signed-off-by: Peter Maydell <[email protected]>