[SRU][Trusty][lts-linux-trusty]Pull Request: Fixes for lp:1519897

[Joseph Salisbury]

This pull request is for Trusty and linux-lts-trusty.

Currently Hyper-V has two policies for deciding when to signal the host:
One based on the ring buffer state and the other based on what the VMBUS client 
driver wants to do. Consider the case when the client wants to explicitly 
control when to signal the host. In this case, if the client were to defer 
signaling, we will not be able to signal the host subsequently when the 
client does want to signal since the ring buffer state will prevent the 
signaling. Implement logic to have only one signaling policy in force for a 
given channel.

The primary fix for this bug is commit 8599846.  However, the other commits
in this pull request are prereqs for Trusty.

Xenial and Wily are also going to need commit 8599846.  However, the prereqs 
will be different and we are still awaiting test results.  A separate pull
request will be done for W and X.

Testing was performed and good results were posted in comment #14.


The following changes since commit 2668f30532b58bdb54c8ab7d818e9ff8fcd50d6a:

  UBUNTU: Ubuntu-3.13.0-76.120 (2016-01-18 09:56:57 +0000)

are available in the git repository at:

  kernel.ubuntu.com:/srv/kernel.ubuntu.com/git/jsalisbury/bugs/lp1519897/ubuntu-trusty.git 

for you to fetch changes up to b15c9fc96bc96ef3711e5c8a96abbef7e3bb8c44:

  Drivers: hv: vmbus: Fix a Host signaling bug (2016-01-22 10:59:57 -0500)

----------------------------------------------------------------
K. Y. Srinivasan (7):
      Drivers: hv: Eliminate the channel spinlock in the callback path
      Drivers: hv: vmbus: Implement per-CPU mapping of relid to channel
      Drivers: hv: vmbus: Suport an API to send pagebuffers with additional control
      Drivers: hv: vmbus: Suport an API to send packet with additional control
      Drivers: hv: vmbus: Export the vmbus_sendpacket_pagebuffer_ctl()
      Drivers: hv: vmbus: Fix a siganlling host signalling issue
      Drivers: hv: vmbus: Fix a Host signaling bug

 drivers/hv/channel.c      | 137 ++++++++++++++++++++++++++++++++++++----------
 drivers/hv/channel_mgmt.c |  52 ++++++++++++++++--
 drivers/hv/connection.c   |  35 +++++++++---
 drivers/hv/hv.c           |   2 +
 drivers/hv/hyperv_vmbus.h |   5 ++
 include/linux/hyperv.h    |  46 ++++++++++++++++
 6 files changed, 236 insertions(+), 41 deletions(-)