RE: [PATCH RFCv2 00/21] Drivers: hv: utils: re-implement the kernel/userspace communication layer

[KY Srinivasan <kys@microsoft.com>]

> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:vkuznets@redhat.com]
> Sent: Wednesday, March 11, 2015 6:29 AM
> To: KY Srinivasan; devel@linuxdriverproject.org
> Cc: Haiyang Zhang; linux-kernel@vger.kernel.org; Dexuan Cui; Radim Krcmar;
> Greg Kroah-Hartman; linux-api@vger.kernel.org
> Subject: [PATCH RFCv2 00/21] Drivers: hv: utils: re-implement the
> kernel/userspace communication layer
> 
> Changes in RFCv2:
> - Preserve backwards compatibility with netlink-speaking daemons. [K. Y.
> Srinivasan]
> - Introduce transport abstraction layer. [K. Y. Srinivasan]
> - Get rid of ioctls [Radim Krcmar]
> - Make the series reviewable by splitting it into smaller patches.
> 
> Anatomy of the series:
> Patches 01 - 07 are cleanup with minor functional change.
> Patch 08 defines the state machine.
> Patches 09-11 convert all 3 drivers to using the state machine.
> Patch 12 fixes a bug in fcopy. This change is going away in Patch 15,  I just
> want to highlight the fix.
> Patch 13 introduces a transport abstraction.
> Patch 14-16 convert all drivers to using the transport abstraction.
> Patches 17-18 switch KVP and VSS daemon to using char devices.
> Patches 19-20 convert FCOPY and VSS to hull handshake (the same we have
> in  KVP). These two can be postponed till we really need to distinguish
> between  different kernels in the daemon code.
> Patch 21 unifies log messages on daemons connect across all drivers and
> moves  these messages to debug level.
> 
> I smoke-tested this series with both old (netlink) and new (char devices)
> daemons and tested the daemon upgrade procedure.
> 
> Original description:
> This series converts kvp/vss daemons to use misc char devices instead of
> netlink for userspace/kernel communication and then updates fcopy to be
> consistent with kvp/vss.
> 
> Userspace/kernel communication via netlink has a number of issues:
> - It is hard for userspace to figure out if the kernel part was loaded or not
>   and this fact can change as there is a way to enable/disable the service from
>   host side. Racy daemon startup is also a problem.
> - When the userspace daemon restarts/dies kernel part doesn't receive a
>   notification.
> - Netlink communication is not stable under heavy load.
> - ...
> 
> Vitaly Kuznetsov (21):
>   Drivers: hv: util: move kvp/vss function declarations to
>     hyperv_vmbus.h
>   Drivers: hv: kvp: reset kvp_context
>   Drivers: hv: kvp: move poll_channel() to hyperv_vmbus.h
>   Drivers: hv: fcopy: process deferred messages when we complete the
>     transaction
>   Drivers: hv: vss: process deferred messages when we complete the
>     transaction
>   Drivers: hv: kvp: rename kvp_work -> kvp_timeout_work
>   Drivers: hv: fcopy: rename fcopy_work -> fcopy_timeout_work
>   Drivers: hv: util: introduce state machine for util drivers
>   Drivers: hv: kvp: switch to using the hvutil_device_state state
>     machine
>   Drivers: hv: vss: switch to using the hvutil_device_state state
>     machine
>   Drivers: hv: fcopy: switch to using the hvutil_device_state state
>     machine
>   Drivers: hv: fcopy: set .owner reference for file operations
>   Drivers: hv: util: introduce hv_utils_transport abstraction
>   Drivers: hv: vss: convert to hv_utils_transport
>   Drivers: hv: fcopy: convert to hv_utils_transport
>   Drivers: hv: kvp: convert to hv_utils_transport
>   Tools: hv: kvp: use misc char device to communicate with kernel
>   Tools: hv: vss: use misc char device to communicate with kernel
>   Drivers: hv: vss: full handshake support
>   Drivers: hv: fcopy: full handshake support
>   Drivers: hv: utils: unify driver registration reporting
> 
>  drivers/hv/Makefile             |   2 +-
>  drivers/hv/hv_fcopy.c           | 287 ++++++++++++++--------------------------
>  drivers/hv/hv_kvp.c             | 192 +++++++++++++--------------
>  drivers/hv/hv_snapshot.c        | 168 +++++++++++++++--------
>  drivers/hv/hv_utils_transport.c | 276
> ++++++++++++++++++++++++++++++++++++++
>  drivers/hv/hv_utils_transport.h |  51 +++++++
>  drivers/hv/hyperv_vmbus.h       |  29 ++++
>  include/linux/hyperv.h          |   8 --
>  include/uapi/linux/hyperv.h     |   8 +-
>  tools/hv/hv_fcopy_daemon.c      |  15 +++
>  tools/hv/hv_kvp_daemon.c        | 166 +++++------------------
>  tools/hv/hv_vss_daemon.c        | 149 ++++++---------------
>  12 files changed, 752 insertions(+), 599 deletions(-)  create mode 100644
> drivers/hv/hv_utils_transport.c  create mode 100644
> drivers/hv/hv_utils_transport.h

Vitaly,

Thank you very much for taking on this project; very well done. I have mostly reviewed the code and I should be
done shortly. Also, I am going to test this code as well. If there are no issues, I will send this out to Greg in my next 
installment of patches.

Regards,

K. Y 
> 
> --
> 1.9.3