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From: Jason Gunthorpe <>
To: Gal Pressman <>
Cc: Leon Romanovsky <>,
	Doug Ledford <>,,
	Alexander Matushevsky <>,
	Firas JahJah <>,
	Yossi Leybovich <>
Subject: Re: [PATCH for-next] RDMA/efa: Move provider specific attributes to ucontext allocation response
Date: Wed, 17 Jun 2020 12:36:38 -0300	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Tue, Jun 16, 2020 at 08:44:37PM +0300, Gal Pressman wrote:
> On 16/06/2020 12:38, Leon Romanovsky wrote:
> > On Tue, Jun 16, 2020 at 11:53:11AM +0300, Gal Pressman wrote:
> >> On 16/06/2020 9:30, Leon Romanovsky wrote:
> >>> On Mon, Jun 15, 2020 at 10:59:20AM +0300, Gal Pressman wrote:
> >>>> Provider specific attributes which are necessary for the userspace
> >>>> functionality should be part of the alloc ucontext response, not query
> >>>> device. This way a userspace provider could work without issuing a query
> >>>> device verb call. However, the fields will remain in the query device
> >>>> ABI in order to maintain backwards compatibility.
> >>>
> >>> I don't really understand why "should be ..."? Device properties exposed
> >>> here are per-device and will be equal to all ucontexts, so instead of
> >>> doing one very fast system call, you are "punishing" every ucontext
> >>> call.
> >>
> >> I talked about it with Jason in the past, the query device verb is intended to
> >> follow the IBA verb, alloc ucontext should return driver specific data that's
> >> required to operate the user space provider.
> >> A query device call should not be mandatory to load the provider.
> > 
> > Why? query_device is declared as mandatory verb for any provider, so
> > anyway all in-the-tree RDMA drivers will have such verb.
> I don't think the concern here is if the verb exists or not, my understanding is
> that query device should be used for IBA query device attributes, not other
> provider specific stuff.
> Jason, want to chime in with your thoughts?

query_device should be used to implement the ibverb query_device and

It should only return rdma-core defined common stuff because that is
what that verb does - there is no reason to return driver specific
things as there is nothing the driver can do with it.

The only exception might be some provider specific query_device dv
that needs more information.

query_device should not be used as some two-part
create_context. Information related only to create_context that is not
already exposed to query_device should not be added to query_device
only for create_context's use.

Similarly, information in query_device should not be duplicated into
create_context just to save a system call.


  parent reply	other threads:[~2020-06-17 15:36 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-15  7:59 Gal Pressman
2020-06-16  6:30 ` Leon Romanovsky
2020-06-16  8:53   ` Gal Pressman
2020-06-16  9:38     ` Leon Romanovsky
2020-06-16 17:44       ` Gal Pressman
2020-06-17  4:55         ` Leon Romanovsky
2020-06-17 15:36         ` Jason Gunthorpe [this message]
2020-06-17 17:49           ` Gal Pressman
2020-06-18 11:30             ` Gal Pressman
2020-06-25 10:53 ` Gal Pressman

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