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, April 8, 2015 9:01 AM
> To: KY Srinivasan
> Cc: devel@linuxdriverproject.org; Haiyang Zhang; linux-
> kernel@vger.kernel.org; Dexuan Cui; Radim Krcmar; Greg Kroah-Hartman;
> linux-api@vger.kernel.org
> Subject: Re: [PATCH RFCv2 00/21] Drivers: hv: utils: re-implement the
> kernel/userspace communication layer
> 
> KY Srinivasan <kys@microsoft.com> writes:
> 
> >> -----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.
> 
> Hi K.Y.,
> 
> I don't mean to rush or anything but please let me know if I need to do
> something with this series (e.g. fix something, rebase/resend it,...) to
> get it applied.

Sorry for the delay Vitaly. I finally was able to test it; please resend the patch-set that can apply on the current tip.

Regards,

K. Y
> 
> Thanks,
> 
> --
>   Vitaly