Merge remote-tracking branch 'remotes/mst/tags/for_upstream' into staging

virtio, pc: fixes, cleanups

A bunch of fixes all over the place.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

# gpg: Signature made Thu 25 Jul 2019 16:19:33 BST
# gpg:                using RSA key 281F0DB8D28D5469
# gpg: Good signature from "Michael S. Tsirkin <mst@kernel.org>" [full]
# gpg:                 aka "Michael S. Tsirkin <mst@redhat.com>" [full]
# Primary key fingerprint: 0270 606B 6F3C DF3D 0B17  0970 C350 3912 AFBE 8E67
#      Subkey fingerprint: 5D09 FD08 71C8 F85B 94CA  8A0D 281F 0DB8 D28D 5469

* remotes/mst/tags/for_upstream:
  virtio-balloon: free pbp more aggressively
  virtio-balloon: don't track subpages for the PBP
  virtio-balloon: Use temporary PBP only
  virtio-balloon: Rework pbp tracking data
  virtio-balloon: Better names for offset variables in inflate/deflate code
  virtio-balloon: Simplify deflate with pbp
  virtio-balloon: Fix QEMU crashes on pagesize > BALLOON_PAGE_SIZE
  virtio-balloon: Fix wrong sign extension of PFNs
  i386/acpi: show PCI Express bus on pxb-pcie expanders
  ioapic: kvm: Skip route updates for masked pins
  i386/acpi: fix gint overflow in crs_range_compare
  docs: clarify multiqueue vs multiple virtqueues

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 17 insertions, 0 deletions

diff --git a/docs/interop/vhost-user.rst b/docs/interop/vhost-user.rst
index 5750668aba..7827b710aa 100644
--- a/docs/interop/vhost-user.rst
+++ b/docs/interop/vhost-user.rst
@@ -324,6 +324,15 @@ must support changing some configuration aspects on the fly.
 Multiple queue support
 ----------------------
 
+Many devices have a fixed number of virtqueues.  In this case the master
+already knows the number of available virtqueues without communicating with the
+slave.
+
+Some devices do not have a fixed number of virtqueues.  Instead the maximum
+number of virtqueues is chosen by the slave.  The number can depend on host
+resource availability or slave implementation details.  Such devices are called
+multiple queue devices.
+
 Multiple queue support allows the slave to advertise the maximum number of
 queues.  This is treated as a protocol extension, hence the slave has to
 implement protocol features first. The multiple queues feature is supported
@@ -339,6 +348,14 @@ queue in the sent message to identify a specified queue.
 The master enables queues by sending message ``VHOST_USER_SET_VRING_ENABLE``.
 vhost-user-net has historically automatically enabled the first queue pair.
 
+Slaves should always implement the ``VHOST_USER_PROTOCOL_F_MQ`` protocol
+feature, even for devices with a fixed number of virtqueues, since it is simple
+to implement and offers a degree of introspection.
+
+Masters must not rely on the ``VHOST_USER_PROTOCOL_F_MQ`` protocol feature for
+devices with a fixed number of virtqueues.  Only true multiqueue devices
+require this protocol feature.
+
 Migration
 ---------