linux-kernel - Re: [Patch v7 21/22] CIFS: SMBD: Upper layer performs SMB read via RDMA write through memory registration

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Message-ID: <f9c791af-28d0-5107-e41a-31eee03cbda0@samba.org>
Date:   Sun, 23 Sep 2018 23:24:27 +0200
From:   Stefan Metzmacher <metze@...ba.org>
To:     Tom Talpey <tom@...pey.com>,
        Long Li <longli@...hange.microsoft.com>,
        Steve French <sfrench@...ba.org>, linux-cifs@...r.kernel.org,
        samba-technical@...ts.samba.org, linux-kernel@...r.kernel.org,
        linux-rdma@...r.kernel.org, Christoph Hellwig <hch@...radead.org>,
        Tom Talpey <ttalpey@...rosoft.com>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>
Subject: Re: [Patch v7 21/22] CIFS: SMBD: Upper layer performs SMB read via
 RDMA write through memory registration

Hi Tom,

>> I just tested that setting:
>>
>> mr->iova &= (PAGE_SIZE - 1);
>> mr->iova |= 0xFFFFFFFF00000000;
>>
>> after the ib_map_mr_sg() and before doing the IB_WR_REG_MR, seems to
>> work.
> 
> Good! As you know, we were concerned about it after seeing that
> the ib_dma_map_sg() code was unconditionally setting it to the
> dma_mapped address. By salting those FFFF's with varying data,
> this should give your FRWR regions stronger integrity in addition
> to not leaking kernel "addresses" to the wire.

Just wondering... Isn't the thing we use called FRMR?

metze



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