From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261588AbVF2QKP (ORCPT ); Wed, 29 Jun 2005 12:10:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261575AbVF2QHm (ORCPT ); Wed, 29 Jun 2005 12:07:42 -0400 Received: from sj-iport-3-in.cisco.com ([171.71.176.72]:2359 "EHLO sj-iport-3.cisco.com") by vger.kernel.org with ESMTP id S261564AbVF2QGY (ORCPT ); Wed, 29 Jun 2005 12:06:24 -0400 X-IronPort-AV: i="3.93,242,1115017200"; d="scan'208"; a="284267518:sNHT27005680" To: Andrew Morton Cc: linux-kernel@vger.kernel.org, openib-general@openib.org Subject: Re: [PATCH 12/16] IB uverbs: add mthca user PD support X-Message-Flag: Warning: May contain useful information References: <2005628163.gtJFW6uLUrGQteys@cisco.com> <2005628163.px5sYyzsYWf21dJY@cisco.com> <20050628170718.0b2a9cad.akpm@osdl.org> From: Roland Dreier Date: Wed, 29 Jun 2005 09:06:22 -0700 Message-ID: <52slz1f8qp.fsf@topspin.com> User-Agent: Gnus/5.1006 (Gnus v5.10.6) XEmacs/21.4 (Jumbo Shrimp, linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Andrew> What is a userspace protection domain? A protection domain is an abstraction enforced by IB hardware -- loosely put, every resource (work queue, memory region, etc) in put in a PD when it is created, and different resources can only see each other if they belong to the same PD. As an example, PDs are needed because IB allows unprivileged processes to directly post requests to work queues. Work requests refer to memory regions by memory keys (32 bit cookies). Without PDs, a process could get access to another process's memory region if it could guess the 32-bit key -- with PDs, it can't because the other process's memory region will be in a different PD from its work queue. - R.