[PATCH 0/4] hv: utils: propagate state to interrupt thread

[Olaf Hering <olaf@aepfle.de>]

The Copy-VMFile cmdlet on the host may fail because the guest fcopy
driver state machine gets out of sync. This happens because the ->state
and ->context variables are accessed by the main thread and from
interrupt context. If an interrupt happens between fcopy_respond_to_host
and hv_poll_channel in fcopy_write, then hv_fcopy_onchannelcallback
called from that interrupt sees still state HVUTIL_USERSPACE_RECV. It
updates the context, but fcopy_write will not notice that update and
hv_poll_channel gets called with an empty context.  As a result
hv_fcopy_daemon gets no more data. After a timeout Copy-VMFile fails
with timeout.

In my initial testing for a fix I put a "mb()" after the last .state
change in fcopy_write. But this series implementes read/write memory
barriers as needed. Let me know if this is overdoing things.

Olaf

Olaf Hering (4):
  hv: add helpers to handle hv_util device state
  hv: fcopy: use wrapper to propate state
  hv: kvp: use wrapper to propate state
  hv: vss: use wrapper to propate state

 drivers/hv/hv_fcopy.c     | 36 ++++++++++++++++++++----------------
 drivers/hv/hv_kvp.c       | 38 +++++++++++++++++++++-----------------
 drivers/hv/hv_snapshot.c  | 37 ++++++++++++++++++++-----------------
 drivers/hv/hyperv_vmbus.h | 12 ++++++++++++
 4 files changed, 73 insertions(+), 50 deletions(-)