From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Hemminger <stephen@networkplumber.org>
Subject: Re: [RFC PATCH] igb_uio: issue FLR during open and
 release of device file
Date: Wed, 31 May 2017 08:30:10 -0700
Message-ID: <20170531083010.228859c3@xeon-e3>
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Cc: Shijith Thotton <shijith.thotton@caviumnetworks.com>, Gregory Etelson
 <gregory@weka.io>, dev@dpdk.org, Qi Zhang <qi.z.zhang@intel.com>, Wenzhuo
 Lu <wenzhuo.lu@intel.com>, Thomas Monjalon <thomas@monjalon.net>, Jianfeng
 Tan <jianfeng.tan@intel.com>
To: Ferruh Yigit <ferruh.yigit@intel.com>
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On Wed, 31 May 2017 13:20:08 +0100
Ferruh Yigit <ferruh.yigit@intel.com> wrote:

> On 5/31/2017 12:09 PM, Shijith Thotton wrote:
> > Set UIO info device file operations open and release. Call pci reset
> > function inside open and release to clear device state at start and
> > end. Copied this behaviour from vfio_pci kernel module code. With this
> > change, it is not mandatory to issue FLR by PMD's during init and close.  
> 
> Cc: Jianfeng Tan <jianfeng.tan@intel.com>
> 
> Jianfeng also implemented following patch:
> http://dpdk.org/dev/patchwork/patch/17495/
> 
> Which also implements release and open ops, for slightly different
> reason (prevent DMA access after app exit), but mainly both are to
> gracefully handle application exit status.
> 
> btw, for Jianfeng's case, can adding pci_clear_master() in release and
> moving pci_set_master() to open help preventing unwanted DMA?
> 
> 
> Gregory,
> 
> Can you please check if this patch fixes your issue?
> 
> Thanks,
> ferruh

pci_reset should stop all DMA. It also clears master status.