Re: [PATCH v3 05/15] xprtrdma: Remove last ib_reg_phys_mr() call site

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On 7/20/2015 4:36 PM, Chuck Lever wrote:

On Jul 20, 2015, at 6:41 PM, Jason Gunthorpe <jgunthorpe@xxxxxxxxxxxxxxxxxxxx> wrote:

On Mon, Jul 20, 2015 at 06:31:11PM -0400, Chuck Lever wrote:

On Jul 20, 2015, at 6:26 PM, Jason Gunthorpe <jgunthorpe@xxxxxxxxxxxxxxxxxxxx> wrote:

On Mon, Jul 20, 2015 at 03:03:11PM -0400, Chuck Lever wrote:
+	iov->length = size;
+	iov->lkey = ia->ri_have_dma_lkey ?
+				ia->ri_dma_lkey : ia->ri_bind_mem->lkey;
+	rb->rg_size = size;
+	rb->rg_owner = NULL;
	return rb;

There is something odd looking about this..

ri_bind_mem is only setup in the RPCRDMA_ALLPHYSICAL and
RPCRDMA_MTHCAFMR cases.

RPCRDMA_FRMR doesn't set it up.

So this code in rpcrdma_alloc_regbuf is never called for the FRMR
case?

If yes, then, how is FRMR working? There is absolutely no reason to
use FRMR to register local send buffers, just use the global all
memory lkey...

If no, then that is an oops?

I’ve tested this code, no oops.

FRWR always uses the DMA lkey. xprtrdma does not use FRWR if
IB_DEVICE_LOCAL_DMA_LKEY is not asserted.

Ah, I see. Ok.

Is there a reason to link FRWR and LOCAL_DMA_LKEY together?

Tom would know.

Tom Talpey or Tom Tucker? I don't think I used a dma_lkey at all
in the original work, but there were some changes later.

I thought not all rnic's supported a dma_lkey. So requiring it
seems like a bad idea, to me.

Just use
the code you have for fmr with frwr to get the lkey, probably move it
to rpcrdma_ia_open .. Physical MR should create a 2nd MR dedicated for
rkey use.

But FMR is not supported by modern mlx5 and cxgb4?
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