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From: Christoph Hellwig <hch@lst.de>
To: Krishnamraju Eraparaju <krishna2@chelsio.com>
Cc: sagi@grimberg.me, linux-rdma@vger.kernel.org,
	Potnuri Bharat Teja <bharat@chelsio.com>,
	Nirranjan Kirubaharan <nirranjan@chelsio.com>,
	linux-nvme@lists.infradead.org,
	Bernard Metzler <BMT@zurich.ibm.com>,
	hch@lst.de
Subject: Re: broken CRCs at NVMeF target with SIW & NVMe/TCP transports
Date: Tue, 17 Mar 2020 13:45:33 +0100	[thread overview]
Message-ID: <20200317124533.GB12316@lst.de> (raw)
In-Reply-To: <20200316162008.GA7001@chelsio.com>

On Mon, Mar 16, 2020 at 09:50:10PM +0530, Krishnamraju Eraparaju wrote:
> 
> I'm seeing broken CRCs at NVMeF target while running the below program
> at host. Here RDMA transport is SoftiWARP, but I'm also seeing the
> same issue with NVMe/TCP aswell.
> 
> It appears to me that the same buffer is being rewritten by the
> application/ULP before getting the completion for the previous requests.
> getting the completion for the previous requests. HW based
> HW based trasports(like iw_cxgb4) are not showing this issue because
> they copy/DMA and then compute the CRC on copied buffer.

For TCP we can set BDI_CAP_STABLE_WRITES.  For RDMA I don't think that
is a good idea as pretty much all RDMA block drivers rely on the
DMA behavior above.  The answer is to bounce buffer the data in
SoftiWARP / SoftRoCE.

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WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Krishnamraju Eraparaju <krishna2@chelsio.com>
Cc: Bernard Metzler <BMT@zurich.ibm.com>,
	sagi@grimberg.me, hch@lst.de, linux-nvme@lists.infradead.org,
	linux-rdma@vger.kernel.org,
	Nirranjan Kirubaharan <nirranjan@chelsio.com>,
	Potnuri Bharat Teja <bharat@chelsio.com>
Subject: Re: broken CRCs at NVMeF target with SIW & NVMe/TCP transports
Date: Tue, 17 Mar 2020 13:45:33 +0100	[thread overview]
Message-ID: <20200317124533.GB12316@lst.de> (raw)
In-Reply-To: <20200316162008.GA7001@chelsio.com>

On Mon, Mar 16, 2020 at 09:50:10PM +0530, Krishnamraju Eraparaju wrote:
> 
> I'm seeing broken CRCs at NVMeF target while running the below program
> at host. Here RDMA transport is SoftiWARP, but I'm also seeing the
> same issue with NVMe/TCP aswell.
> 
> It appears to me that the same buffer is being rewritten by the
> application/ULP before getting the completion for the previous requests.
> getting the completion for the previous requests. HW based
> HW based trasports(like iw_cxgb4) are not showing this issue because
> they copy/DMA and then compute the CRC on copied buffer.

For TCP we can set BDI_CAP_STABLE_WRITES.  For RDMA I don't think that
is a good idea as pretty much all RDMA block drivers rely on the
DMA behavior above.  The answer is to bounce buffer the data in
SoftiWARP / SoftRoCE.

  parent reply	other threads:[~2020-03-17 12:45 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-16 16:20 broken CRCs at NVMeF target with SIW & NVMe/TCP transports Krishnamraju Eraparaju
2020-03-16 16:20 ` Krishnamraju Eraparaju
2020-03-17  9:31 ` Bernard Metzler
2020-03-17  9:31   ` Bernard Metzler
2020-03-17 12:26   ` Tom Talpey
2020-03-17 12:26     ` Tom Talpey
2020-03-17 12:45 ` Christoph Hellwig [this message]
2020-03-17 12:45   ` Christoph Hellwig
2020-03-17 13:17   ` Bernard Metzler
2020-03-17 13:17     ` Bernard Metzler
2020-03-17 16:03   ` Sagi Grimberg
2020-03-17 16:03     ` Sagi Grimberg
2020-03-17 16:29     ` Bernard Metzler
2020-03-17 16:29       ` Bernard Metzler
2020-03-17 16:39       ` Sagi Grimberg
2020-03-17 16:39         ` Sagi Grimberg
2020-03-17 19:17         ` Krishnamraju Eraparaju
2020-03-17 19:17           ` Krishnamraju Eraparaju
2020-03-17 19:33           ` Sagi Grimberg
2020-03-17 19:33             ` Sagi Grimberg
2020-03-17 20:31             ` Krishnamraju Eraparaju
2020-03-17 20:31               ` Krishnamraju Eraparaju
2020-03-18 16:49               ` Sagi Grimberg
2020-03-18 16:49                 ` Sagi Grimberg
2020-03-20 14:35                 ` Krishnamraju Eraparaju
2020-03-20 14:35                   ` Krishnamraju Eraparaju
2020-03-20 20:49                   ` Sagi Grimberg
2020-03-20 20:49                     ` Sagi Grimberg
2020-03-21  4:02                     ` Krishnamraju Eraparaju
2020-03-21  4:02                       ` Krishnamraju Eraparaju

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