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From: Jason Gunthorpe <jgg@ziepe.ca>
To: Bob Pearson <rpearsonhpe@gmail.com>
Cc: Bart Van Assche <bvanassche@acm.org>,
	"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>
Subject: Re: blktest/rxe almost working
Date: Tue, 7 Sep 2021 13:39:39 -0300	[thread overview]
Message-ID: <20210907163939.GW1200268@ziepe.ca> (raw)
In-Reply-To: <9e6783d0-554c-17de-c72f-fae766099480@gmail.com>

On Tue, Sep 07, 2021 at 11:35:17AM -0500, Bob Pearson wrote:

> Interesting. But if that is the case the bigger problem is the ib_map_mr_sg() call which updates the
> mapping. rxe definitely does look at the mr->rkey value but we could fix that. It also looks at the
> mapping which is updated by ib_map_mr_sg(). My impression is that HW also uses this mapping or does
> HW also copy all the FMRs into SRAM?

Yes, real HW has a copy of the DMA list. The sg in the mr struct is
for CPU use only.

It is not OK to use the CPU SG list inside the MR for DMA by HW, it
has to be synchronized with the WR.

> There seems to be an assumption that users will be looking at CQE.

Yes, the kernel has to be driven by CQE, not only for data transfer
but the DMA unmap of the SGL cannot be until after the invalidation
CQE is observed.

Ie the CPU should have two DMA lists active during the invalidation
cycle.

Jason

  reply	other threads:[~2021-09-07 16:39 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-02 21:41 Bob Pearson
2021-09-02 23:38 ` Jason Gunthorpe
2021-09-03 22:18   ` Bob Pearson
2021-09-03 23:13     ` Bart Van Assche
2021-09-04 22:30       ` Jason Gunthorpe
2021-09-05 18:02         ` Bob Pearson
2021-09-07 12:01           ` Jason Gunthorpe
2021-09-07 16:35             ` Bob Pearson
2021-09-07 16:39               ` Jason Gunthorpe [this message]
2021-09-07 16:47                 ` Bob Pearson

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