From owner-freebsd-current@FreeBSD.ORG Wed Jan 11 19:56:53 2012 Return-Path: Delivered-To: freebsd-current@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 3537E106566B; Wed, 11 Jan 2012 19:56:53 +0000 (UTC) (envelope-from avg@FreeBSD.org) Received: from citadel.icyb.net.ua (citadel.icyb.net.ua [212.40.38.140]) by mx1.freebsd.org (Postfix) with ESMTP id 527508FC1E; Wed, 11 Jan 2012 19:56:51 +0000 (UTC) Received: from porto.starpoint.kiev.ua (porto-e.starpoint.kiev.ua [212.40.38.100]) by citadel.icyb.net.ua (8.8.8p3/ICyb-2.3exp) with ESMTP id VAA22037; Wed, 11 Jan 2012 21:56:49 +0200 (EET) (envelope-from avg@FreeBSD.org) Received: from localhost ([127.0.0.1]) by porto.starpoint.kiev.ua with esmtp (Exim 4.34 (FreeBSD)) id 1Rl4Hx-000BAX-HJ; Wed, 11 Jan 2012 21:56:49 +0200 Message-ID: <4F0DE97F.60208@FreeBSD.org> Date: Wed, 11 Jan 2012 21:56:47 +0200 From: Andriy Gapon User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:9.0) Gecko/20111222 Thunderbird/9.0 MIME-Version: 1.0 To: John Baldwin References: <4F0C9D14.60705@FreeBSD.org> <201201111001.04724.jhb@freebsd.org> <4F0DC476.8050509@FreeBSD.org> In-Reply-To: <4F0DC476.8050509@FreeBSD.org> X-Enigmail-Version: undefined Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: freebsd-current@FreeBSD.org Subject: Re: bus dma: a flag/quirk for page zero X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 11 Jan 2012 19:56:53 -0000 on 11/01/2012 19:18 Andriy Gapon said the following: > Actually, I think that on x86 we don't have to do anything special for any memory > allocations that we do, including the bounce pages, as the page zero is excluded > from phys_avail and is not available for normal use. After some additional thinking there is probably no reason to take advantage of this fact. First, it would increase differences with other platforms. Second, it would add a hidden dependency. So it's better to be explicit here. -- Andriy Gapon