Date: Mon, 11 Apr 2005 11:33:42 -0500
From: Troy Benjegerdes <hozer@hozed.org>
To: Roland Dreier <roland@topspin.com>
Cc: linux-kernel@vger.kernel.org, openib-general@openib.org
Subject: Re: [PATCH][RFC][0/4] InfiniBand userspace verbs implementation
Message-ID: <20050411163342.GE26127@kalmia.hozed.org>
References: <200544159.Ahk9l0puXy39U6u6@topspin.com> <20050411142213.GC26127@kalmia.hozed.org> <52mzs51g5g.fsf@topspin.com>
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On Mon, Apr 11, 2005 at 08:34:19AM -0700, Roland Dreier wrote:
>     Troy> How is memory pinning handled? (I haven't had time to read
>     Troy> all the code, so please excuse my ignorance of something
>     Troy> obvious).
> 
> The userspace library calls mlock() and then the kernel does
> get_user_pages().

Is there a check in the kernel that the memory is actually mlock()ed?

What if a malicious (or broken) application does ibv_reg_mr() but
doesn't lock the memory? Does the IB card get a physical address for a
page that might get swapped out?

>     Troy> The old mellanox drivers used to have a hack to call
>     Troy> 'sys_mlock', and promiscuously lock memory any old userspace
>     Troy> application asked for. What is the API for the new uverbs
>     Troy> memory registration, and how will things like memory hotplug
>     Troy> and NUMA page migration be able to unpin pages locked by a
>     Troy> user program?
> 
> The API for uverbs memory registration is ibv_reg_mr(), and right now
> the memory is pinned and that's it.
> 
>  - R.

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