Re: [Qemu-devel] [PATCH 00/10] RFCv3: vhost-user: simple reconnection support

[Yuanhan Liu <yuanhan.liu@linux.intel.com>]

Hi Marc,

I was also thinking we should do it in this way first. That simplfies
things. So, feel free to add:

Tested-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Reviewed-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>

(well, I didn't review the test case carefully).

Thanks.

	--yliu

On Tue, May 10, 2016 at 06:03:50PM +0200, marcandre.lureau@redhat.com wrote:
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
> 
> Hi,
> 
> In a previous series "RFCv2: vhost-user: shutdown and reconnection", I
> proposed to add a new slave request to handle graceful shutdown, for
> both qemu configuration, server or client, while keeping the guest
> running with link down status.
> 
> However, for the simple case where qemu is configured as server, and
> the backend processes packets in order and disconnects, it is possible
> for the backend to recover after reconnection by discarding the qemu
> SET_VRING_BASE value and resuming from the used->index instead. This
> simplifies the reconnection support in this particular situation (it
> would make sense to have the backend declare this behaviour with an
> extra flag)
> 
> The guest won't be notified of link status change and queues may not
> be processed in a timely manner, also qemu may assert if some
> vhost-user commands are happening while the backend is disconnected.
> So the reconnection must happen "quickly enough" here. In order to
> keep the series relatively small, these further problems will be
> addressed later.
> 
> These series demonstrates a simple reconnect support for vubr
> (configured as client and qemu as server), includes some nice to
> have fixes and a simple test.
> 
> Marc-André Lureau (8):
>   vubr: add client mode
>   vubr: workaround stale vring base
>   vhost-user: disconnect on start failure
>   vhost-net: do not crash if backend is not present
>   vhost-net: save & restore vhost-user acked features
>   vhost-net: save & restore vring enable state
>   tests: append i386 tests
>   test: start vhost-user reconnect test
> 
> Tetsuya Mukawa (2):
>   vhost-user: add ability to know vhost-user backend disconnection
>   qemu-char: add qemu_chr_disconnect to close a fd accepted by listen fd
> 
>  hw/net/vhost_net.c        |  39 ++++++++++++++-
>  include/net/net.h         |   1 +
>  include/net/vhost-user.h  |   1 +
>  include/net/vhost_net.h   |   3 ++
>  include/sysemu/char.h     |   7 +++
>  net/vhost-user.c          |  32 +++++++++++-
>  qemu-char.c               |   8 +++
>  tests/Makefile            |   2 +-
>  tests/vhost-user-bridge.c |  45 ++++++++++++-----
>  tests/vhost-user-test.c   | 123 +++++++++++++++++++++++++++++++++++++++-------
>  10 files changed, 228 insertions(+), 33 deletions(-)
> 
> -- 
> 2.7.4