Re: [PATCH V3 1/5] RDMA/core: Transport-independent access flags

[Jason Gunthorpe <jgunthorpe@obsidianresearch.com>]

On Tue, Jul 14, 2015 at 11:50:57PM -0700, 'Christoph Hellwig' wrote:
> On Tue, Jul 14, 2015 at 02:29:43PM -0600, Jason Gunthorpe wrote:
> > local_dma_lkey appears to be global, it works with any PD.
> > 
> > ib_get_dma_mr is tied to a PD, so it cannot replace local_dma_lkey at
> > the struct device level.
> > 
> > ib_alloc_pd is the in-kernel entry point, the UAPI calls
> > device->alloc_pd directly.. So how about the below patch as a starting
> > point?
> 
> This looks perfect to me.  After this we can get rid of the
> ib_get_dma_mr calls outside of ib_alloc_pd, and eventuall move
> setting up ->local_dma_lkey into the HW driver and kill of
> ib_get_dma_mr, IB_DEVICE_LOCAL_DMA_LKEY and device->local_dma_lkey.

Just for clarity, again, we can never do this.

device->local_dma_lkey requires dedicated hardware support. We cannot
create it in software on old hardware. The only option I see is the
different-for-every-PD solution in my patch.

> (especially together with patches removing all other callsites of
> "ib_get_dma_mr(pd, IB_ACCESS_LOCAL_WRITE)".

I might find time to type this in, but I won't be able to find time to
do any testing on the ULPs..

Jason