linux-kernel - Re: [PATCH 1/8] Drivers: hv: kvp: fix IP Failover

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Message-ID: <20160430210436.GA31172@kroah.com>
Date:	Sat, 30 Apr 2016 14:04:36 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	"K. Y. Srinivasan" <kys@...rosoft.com>
Cc:	linux-kernel@...r.kernel.org, devel@...uxdriverproject.org,
	olaf@...fle.de, apw@...onical.com, vkuznets@...hat.com,
	jasowang@...hat.com
Subject: Re: [PATCH 1/8] Drivers: hv: kvp: fix IP Failover

On Tue, Apr 05, 2016 at 04:57:40PM -0700, K. Y. Srinivasan wrote:
> From: Vitaly Kuznetsov <vkuznets@...hat.com>
> 
> Hyper-V VMs can be replicated to another hosts and there is a feature to
> set different IP for replicas, it is called 'Failover TCP/IP'. When
> such guest starts Hyper-V host sends it KVP_OP_SET_IP_INFO message as soon
> as we finish negotiation procedure. The problem is that it can happen (and
> it actually happens) before userspace daemon connects and we reply with
> HV_E_FAIL to the message. As there are no repetitions we fail to set the
> requested IP.
> 
> Solve the issue by postponing our reply to the negotiation message till
> userspace daemon is connected. We can't wait too long as there is a
> host-side timeout (cca. 75 seconds) and if we fail to reply in this time
> frame the whole KVP service will become inactive. The solution is not
> ideal - if it takes userspace daemon more than 60 seconds to connect
> IP Failover will still fail but I don't see a solution with our current
> separation between kernel and userspace parts.
> 
> Other two modules (VSS and FCOPY) don't require such delay, leave them
> untouched.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
> Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
> ---
>  drivers/hv/hv_kvp.c       |   31 +++++++++++++++++++++++++++++++
>  drivers/hv/hyperv_vmbus.h |    5 +++++
>  2 files changed, 36 insertions(+), 0 deletions(-)

This series doesn't apply to my tree :(