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Groups > linux.kernel > #1673090

Re: New NTB API Issue

From Logan Gunthorpe <logang@deltatee.com>
Newsgroups linux.kernel
Subject Re: New NTB API Issue
Date 2017-06-23 00:20 +0200
Message-ID <tViCd-2bj-9@gated-at.bofh.it> (permalink)
References (1 earlier) <tUb9M-7kQ-17@gated-at.bofh.it> <tVcZQ-77P-5@gated-at.bofh.it> <tVfkZ-8tU-3@gated-at.bofh.it> <tVfkZ-8tU-1@gated-at.bofh.it> <tViCd-2bj-7@gated-at.bofh.it>
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On 6/22/2017 4:12 PM, Allen Hubbe wrote:
> The resource size given by peer_mw_get_addr might be different than the max_size given by ntb_mw_get_align.
>
> I am most familiar with the ntb_hw_intel driver and that type of ntb hardware.  The peer_mw_get_addr size is of the primary bar on the side to be the source of the translated writes (or reads).  In b2b topology, at least, the first translation of that write lands it on the secondary bar of the peer ntb.  That size of that bar could different than the first.  The second translation lands the write in memory (eg).  So, the end-to-end translation is limited by the first AND second sizes.
>
> The first point is, the *max_size returned by intel_ntb_mw_get_align looks wrong.  That should be the size of the secondary bar, not the resource size of the primary bar, of that device.
>
> The second point is, because the sizes returned by peer_mw_get_addr, and ntb_mw_get_align, may be different, the two sides should communicate and reconcile the address and size information when setting up the translations.

Ok, that makes some sense. So drivers that don't need this should return 
-1 or something like that? Though, I'd still suggest that until a driver 
actually needs this, and it's implemented correctly in the clients, we 
should leave it out.

Any thoughts on changing the semantics of mw_get_align so it must be 
called with the link up?

Logan

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Thread

New NTB API Issue Logan Gunthorpe <logang@deltatee.com> - 2017-06-22 18:20 +0200
  Re: New NTB API Issue Logan Gunthorpe <logang@deltatee.com> - 2017-06-22 20:50 +0200
    RE: New NTB API Issue "Allen Hubbe" <Allen.Hubbe@dell.com> - 2017-06-23 00:20 +0200
      Re: New NTB API Issue Logan Gunthorpe <logang@deltatee.com> - 2017-06-23 00:20 +0200
        RE: New NTB API Issue "Allen Hubbe" <Allen.Hubbe@dell.com> - 2017-06-23 00:50 +0200
          Re: New NTB API Issue Logan Gunthorpe <logang@deltatee.com> - 2017-06-23 00:50 +0200
            RE: New NTB API Issue "Allen Hubbe" <Allen.Hubbe@dell.com> - 2017-06-23 15:20 +0200
              Re: New NTB API Issue Logan Gunthorpe <logang@deltatee.com> - 2017-06-23 19:00 +0200
                RE: New NTB API Issue "Allen Hubbe" <Allen.Hubbe@dell.com> - 2017-06-23 21:10 +0200
                Re: New NTB API Issue Logan Gunthorpe <logang@deltatee.com> - 2017-06-23 22:40 +0200
                RE: New NTB API Issue "Allen Hubbe" <Allen.Hubbe@dell.com> - 2017-06-24 00:10 +0200
                Re: New NTB API Issue Logan Gunthorpe <logang@deltatee.com> - 2017-06-24 01:10 +0200
                Re: New NTB API Issue Serge Semin <fancer.lancer@gmail.com> - 2017-06-23 23:50 +0200
                Re: New NTB API Issue Logan Gunthorpe <logang@deltatee.com> - 2017-06-24 00:10 +0200
                RE: New NTB API Issue "Allen Hubbe" <Allen.Hubbe@dell.com> - 2017-06-24 00:10 +0200
  RE: New NTB API Issue "Allen Hubbe" <Allen.Hubbe@dell.com> - 2017-06-22 20:50 +0200

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