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

Steve Wise
2015-07-14T21:01:04Z

> -----Original Message-----
> From: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org [mailto:linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org] On Behalf Of Steve Wise
> Sent: Tuesday, July 14, 2015 3:51 PM
> To: 'Jason Gunthorpe'
> Cc: 'Christoph Hellwig'; 'Sagi Grimberg'; 'Steve Wise'; 'Tom Talpey'; 'Doug Ledford'; sagig-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org; ogerlitz-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org;
> roid-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org; linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; eli-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org; target-devel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org;
> trond.myklebust-7I+n7zu2hftEKMMhf/gKZA@public.gmane.org; bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org; 'Oren Duer'
> Subject: RE: [PATCH V3 1/5] RDMA/core: Transport-independent access flags
>
>
>
> > -----Original Message-----
> > From: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org [mailto:linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org] On Behalf Of Jason Gunthorpe
> > Sent: Tuesday, July 14, 2015 3:42 PM
> > To: Steve Wise
> > Cc: 'Christoph Hellwig'; 'Sagi Grimberg'; 'Steve Wise'; 'Tom Talpey'; 'Doug Ledford'; sagig-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org; ogerlitz-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org;
> > roid-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org; linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; eli-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org; target-devel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org;
> > trond.myklebust-7I+n7zu2hftEKMMhf/gKZA@public.gmane.org; bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org; 'Oren Duer'
> > Subject: Re: [PATCH V3 1/5] RDMA/core: Transport-independent access flags
> >
> > On Tue, Jul 14, 2015 at 02:58:23PM -0500, Steve Wise wrote:
> > > The local_dma_lkey can be used in any rdma sge that requires an
> > > lkey.
> >
> > No, this is where iWarp doesn't follow the generic API - a local dma
> > lkey cannot be used with iWarp's RDMA_READ WR lkey. In effect RDMA
> > READ requires an *rkey* (confusingly stuck into the lkey slot) for
> > iWarp. (Right?)
> >
>
> Right, a local_dma_lkey is not an rkey, and iwarp requires the rkey for the read destination MR. Further that rkey needs
> REMOTE_WRITE.
>

BTW: What use is an IB rkey with no REMOTE_ flags set? Can it be used somehow differently than the associated lkey?

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