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Subject: Re: [PATCH V5 2/2] nvme-pci: fixup the timeout case when reset is
 ongoing
To:     Keith Busch <keith.busch@intel.com>
Cc:     sagi@grimberg.me, james.smart@broadcom.com,
        linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org,
        axboe@fb.com, maxg@mellanox.com, hch@lst.de
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From:   "jianchao.wang" <jianchao.w.wang@oracle.com>
Message-ID: <23b3ea15-aed0-3b2f-e02f-124fe6fdf618@oracle.com>
Date:   Fri, 19 Jan 2018 14:53:37 +0800
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Hi Keith

Thanks for your kindly reminding.

On 01/19/2018 02:05 PM, Keith Busch wrote:
>>> The driver may be giving up on the command here, but that doesn't mean
>>> the controller has. We can't just end the request like this because that
>>> will release the memory the controller still owns. We must wait until
>>> after nvme_dev_disable clears bus master because we can't say for sure
>>> the controller isn't going to write to that address right after we end
>>> the request.
>>>
>> Yes, but the controller is going to be reseted or shutdown at the moment,
>> even if the controller accesses a bad address and goes wrong, everything will
>> be ok after reset or shutdown. :)
> Hm, I don't follow. DMA access after free is never okay.
Yes, this may cause unexpected memory corruption.

Thanks
Jianchao