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

[Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>]

On 7/20/2015 5:42 PM, Jason Gunthorpe wrote:
> On Mon, Jul 20, 2015 at 05:41:27PM -0500, Steve Wise wrote:
>>> B) why bother to check? Are machines with <4GB interesting, and worth
>>> supporting a special optimization?
>> No, but cxgb3 is still interesting to user applications, and perhaps NFSRDMA using FRMRs.
> Doesn't look like the NFS client will work. It requires an all
> physical memory lkey for SEND and RECV buffers..
>
> Jason
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Looks like cxgb3 supports LOCAL_DMA_LKEY and MEM_MGT_EXTENSIONS so dma 
mrs aren't required for NFSRDMA:

t4:~/linux-2.6/drivers/infiniband/hw/cxgb3 # grep IB_DEVICE_ iwch_provider.c
         strlcpy(dev->ibdev.name, "cxgb3_%d", IB_DEVICE_NAME_MAX);
         dev->device_cap_flags = IB_DEVICE_LOCAL_DMA_LKEY |
                                 IB_DEVICE_MEM_WINDOW |
                                 IB_DEVICE_MEM_MGT_EXTENSIONS;

So cxgb3 can still support NFSRDMA and user verbs w/o get_dma_mr(). I'll 
submit a patch soon to only support get_dma_mr() if unsigned long is 4 
bytes...

Steve.

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