Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752614Ab0DIWL7 (ORCPT ); Fri, 9 Apr 2010 18:11:59 -0400 Received: from mail-gw0-f46.google.com ([74.125.83.46]:55890 "EHLO mail-gw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752038Ab0DIWLy convert rfc822-to-8bit (ORCPT ); Fri, 9 Apr 2010 18:11:54 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=bLT3Jzk9RwkyYBJbBIlVntSId7YqH5673NEQ+gkai8PQKbJ71IZIelL+ReNu2DN8qA i8F+OgcfLpa+HwinEMxw6uhCz6RipBQ+8QTAi8DySGcPSh8H3ho9DKEVXtDTXtGTItp7 mw08IlelZTBTM7voKPUCOhpDDblE6Dtxhqyzg= MIME-Version: 1.0 In-Reply-To: References: <20100409202533.GA8983@phenom.dumpdata.com> Date: Fri, 9 Apr 2010 16:11:52 -0600 Message-ID: Subject: Re: [LKML] Re: USB transfer_buffer allocations on 64bit systems From: Robert Hancock To: Alan Stern Cc: Konrad Rzeszutek Wilk , Pedro Ribeiro , Daniel Mack , linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Greg KH , alsa-devel@alsa-project.org, linux-usb@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1392 Lines: 32 On Fri, Apr 9, 2010 at 3:23 PM, Alan Stern wrote: > On Fri, 9 Apr 2010, Konrad Rzeszutek Wilk wrote: > >> On Fri, Apr 09, 2010 at 03:34:06PM -0400, Alan Stern wrote: >> > On Fri, 9 Apr 2010, Pedro Ribeiro wrote: >> > >> > > > The DMA pointers do indeed look sane. I wanted to take a deeper look at >> > > > this and set up a 64bit system today. However, I fail to see the problem >> > > > here. Pedro, how much RAM does your machine have installed? >> > >> > > It has 4 GB. >> > >> > That means DMA mapping cannot be the cause of the problem. ?:-( >> >> That isn't entirely true. The BIOS usually allocates a 256 MB ACPI/PCI hole >> that is under the 4GB. >> >> So end up with 3.7 GB, then the 256MB hole, and then right above the 4GB >> you the the remaining memory: 4.3GB. > > How can Pedro find out what physical addresses are in use on his > system? If you have 4GB of RAM then almost certainly you have memory located at addresses over 4GB. If you look at the e820 memory map printed at the start of dmesg on bootup and see entries with addresses of 100000000 or higher reported as usable, then this is the case. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/