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Date: Tue, 14 Jul 2015 12:45:12 -0700
From: "'Christoph Hellwig'" <hch@infradead.org>
To: Steve Wise <swise@opengridcomputing.com>
Cc: "'Sagi Grimberg'" <sagig@dev.mellanox.co.il>,
        "'Steve Wise'" <swise@ogc.us>,
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Subject: Re: [PATCH V3 1/5] RDMA/core: Transport-independent access flags
Message-ID: <20150714194512.GA25887@infradead.org>
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On Tue, Jul 14, 2015 at 02:25:50PM -0500, Steve Wise wrote:
> if (device_supports_fastreg && device_supports_signature)
>         use FRMR
> else
>         use DMAMR
> 
> Shouldn't we just recode it this way?
> 
> if (device_supports_fastreg)
>         use FRMR
> else
>         use DMAMR

How does IB_DEVICE_LOCAL_DMA_LKEY (and ->local_dma_lkey) play into
this?  Seems like that should be the preferred option if supported.

Interestingly enough various iWarp driver seem to support this option,
what's the story behind that?  The (to me surprising) conclusion on
the list was that iWarp would always need a memory regireations that
also allows remove writes even for lkeys, but from looking at the
users of IB_DEVICE_LOCAL_DMA_LKEY / local_dma_lkey that seem to
prefer that over creating a MR.