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From: Bob Pearson <rpearsonhpe@gmail.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Leon Romanovsky <leon@kernel.org>,
	zyjzyj2000@gmail.com, linux-rdma@vger.kernel.org
Subject: Re: [PATCH for-next 0/6] RDMA/rxe: Fix potential races
Date: Tue, 19 Oct 2021 17:51:22 -0500	[thread overview]
Message-ID: <8f8c6aa3-b13e-16b8-a0ac-e68fe327a660@gmail.com> (raw)
In-Reply-To: <20211019184327.GX2744544@nvidia.com>

On 10/19/21 1:43 PM, Jason Gunthorpe wrote:
> On Tue, Oct 19, 2021 at 11:35:30AM -0500, Bob Pearson wrote:
> 
>> Take a look at the note I copied you on more recently. There is some
>> progress but not complete elimination of rxe_pool. There is another
>> project suggested by Jason which is replacing red black trees by
>> xarrays as an alternative approach to indexing rdma objects.  This
>> would still duplicate the indexing done by rdma-core. A while back I
>> looked at trying to reuse the rdma-core indexing but no effort was
>> made to make that easy.
> 
> I have no expecation that a driver can re-use the various rdma-core
> indexes.. that is not what they are for, and they have a different
> lifetime semantic from wha the driver needs.
> 
>> of the APIs are private to rdma-core. These indices are managed by
>> the rxe driver for use as lkeys/rkeys, qpns, srqns, and more
>> recently address handles. xarrays seem to be more efficient when the
>> indices are fairly compact. There is a suggestion that IB and RoCE
>> should attempt to make indices that are visible on the network more
>> sparse. Nothing will make them secure but they could be a lot more
>> secure than they are currently. I believe mlx5 is now using random
>> keys for this reason.
> 
> Only qpn really benifits from something like this, and it is more
> about maximum lifetime before qpn re-use which is a cyclic allocating
> xarray.
> 
> Jason
> 

Thanks. I had given up long ago on using the rdma-core indices. Leon would like
to get rid of rxe pools. Actually (I just checked) there is only one remaining
object type that is not already allocated in rdma-core and that is MR. (The multicast
groups are a special case and not really in the same league as PD, QP, CQ, etc. They
probably should just be replaced with open coded kzalloc/kfree. They are not shared
or visible to rdma-core.) So with this exception the pools are really just a way to add
indices to objects which can be done cleanly with xarrays (I have a version that
already does this and it works fine. No performance difference with red-black trees
though. Still looking to get rid of the spinlocks and use the rcu locking in xarrays.)

Bob

      reply	other threads:[~2021-10-19 22:51 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-10 23:59 [PATCH for-next 0/6] RDMA/rxe: Fix potential races Bob Pearson
2021-10-10 23:59 ` [PATCH for-next 1/6] RDMA/rxe: Make rxe_alloc() take pool lock Bob Pearson
2021-10-20 23:16   ` Jason Gunthorpe
2021-10-21 17:46     ` Bob Pearson
2021-10-25 12:43       ` Jason Gunthorpe
2021-10-25 18:48         ` Robert Pearson
2021-10-10 23:59 ` [PATCH for-next 2/6] RDMA/rxe: Copy setup parameters into rxe_pool Bob Pearson
2021-10-10 23:59 ` [PATCH for-next 3/6] RDMA/rxe: Save object pointer in pool element Bob Pearson
2021-10-20 23:20   ` Jason Gunthorpe
2021-10-21 17:21     ` Bob Pearson
2021-10-25 15:40       ` Jason Gunthorpe
2021-10-10 23:59 ` [PATCH for-next 4/6] RDMA/rxe: Combine rxe_add_index with rxe_alloc Bob Pearson
2021-10-10 23:59 ` [PATCH for-next 5/6] RDMA/rxe: Combine rxe_add_key " Bob Pearson
2021-10-10 23:59 ` [PATCH for-next 6/6] RDMA/rxe: Fix potential race condition in rxe_pool Bob Pearson
2021-10-20 23:23   ` Jason Gunthorpe
2021-10-12  6:34 ` [PATCH for-next 0/6] RDMA/rxe: Fix potential races Leon Romanovsky
2021-10-12 20:19   ` Bob Pearson
2021-10-19 13:07     ` Leon Romanovsky
2021-10-19 16:35       ` Bob Pearson
2021-10-19 18:43         ` Jason Gunthorpe
2021-10-19 22:51           ` Bob Pearson [this message]

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