netdev - Re: [PATCH net] net/mlx4_core: Avoid delays during VF driver device shutdown

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Date:   Thu, 16 Mar 2017 20:16:00 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     tariqt@...lanox.com
Cc:     netdev@...r.kernel.org, eranbe@...lanox.com,
        jackm@....mellanox.co.il
Subject: Re: [PATCH net] net/mlx4_core: Avoid delays during VF driver
 device shutdown

From: Tariq Toukan <tariqt@...lanox.com>
Date: Mon, 13 Mar 2017 19:29:08 +0200

> From: Jack Morgenstein <jackm@....mellanox.co.il>
> 
> Some Hypervisors detach VFs from VMs by instantly causing an FLR event
> to be generated for a VF.
> 
> In the mlx4 case, this will cause that VF's comm channel to be disabled
> before the VM has an opportunity to invoke the VF device's "shutdown"
> method.
> 
> For such Hypervisors, there is a race condition between the VF's
> shutdown method and its internal-error detection/reset thread.
> 
> The internal-error detection/reset thread (which runs every 5 seconds) also
> detects a disabled comm channel. If the internal-error detection/reset
> flow wins the race, we still get delays (while that flow tries repeatedly
> to detect comm-channel recovery).
> 
> The cited commit fixed the command timeout problem when the
> internal-error detection/reset flow loses the race.
> 
> This commit avoids the unneeded delays when the internal-error
> detection/reset flow wins.
> 
> Fixes: d585df1c5ccf ("net/mlx4_core: Avoid command timeouts during VF driver device shutdown")
> Signed-off-by: Jack Morgenstein <jackm@....mellanox.co.il>
> Reported-by: Simon Xiao <sixiao@...rosoft.com>
> Signed-off-by: Tariq Toukan <tariqt@...lanox.com>

Applied.