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Date: Thu, 18 Oct 2018 19:07:57 +0200
From: "'gregkh@linuxfoundation.org'" <gregkh@linuxfoundation.org>
To: Dexuan Cui <decui@microsoft.com>
Cc: "'stable@vger.kernel.org'" <stable@vger.kernel.org>,
        'Wang Jian' <jianjian.wang1@gmail.com>,
        Long Li <longli@microsoft.com>,
        KY Srinivasan <kys@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Josh Poulson <jopoulso@microsoft.com>,
        "Michael Kelley (EOSG)" <Michael.H.Kelley@microsoft.com>
Subject: Re: [PATCH 4/4] [for linux-4.4.y only] HV: properly delay KVP
 packets when negotiation is in progress
Message-ID: <20181018170757.GI11159@kroah.com>
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On Wed, Oct 17, 2018 at 01:23:26AM +0000, Dexuan Cui wrote:
> 
> The host may send multiple negotiation packets
> (due to timeout) before the KVP user-mode daemon
> is connected. KVP user-mode daemon is connected.
> We need to defer processing those packets
> until the daemon is negotiated and connected.
> It's okay for guest to respond
> to all negotiation packets.
> 
> In addition, the host may send multiple staged
> KVP requests as soon as negotiation is done.
> We need to properly process those packets using one
> tasklet for exclusive access to ring buffer.
> 
> This patch is based on the work of
> Nick Meier <Nick.Meier@microsoft.com>.
> 
> Signed-off-by: Long Li <longli@microsoft.com>
> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> 
> The above is the original changelog of
> a3ade8cc474d ("HV: properly delay KVP packets when negotiation is in progress"
> 
> Here I re-worked the original patch because the mainline version
> can't work for the linux-4.4.y branch, on which channel->callback_event
> doesn't exist yet. In the mainline, channel->callback_event was added by:
> 631e63a9f346 ("vmbus: change to per channel tasklet"). Here we don't want
> to backport it to v4.4, as it requires extra supporting changes and fixes,
> which are unnecessary as to the KVP bug we're trying to resolve.
> 
> NOTE: before this patch is used, we should cherry-pick the other related
> 3 patches from the mainline first:
> 
> The background of this backport request is that: recently Wang Jian reported
> some KVP issues: https://github.com/LIS/lis-next/issues/593:
> e.g. the /var/lib/hyperv/.kvp_pool_* files can not be updated, and sometimes
> if the hv_kvp_daemon doesn't timely start, the host may not be able to query
> the VM's IP address via KVP.
> 
> Reported-by: Wang Jian <jianjian.wang1@gmail.com>
> Tested-by: Wang Jian <jianjian.wang1@gmail.com>
> Signed-off-by: Dexuan Cui <decui@microsoft.com>


This should also be added to 4.9.y, right?

thanks,

greg k-h