From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lb0-f174.google.com ([209.85.217.174]:50853 "EHLO mail-lb0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752976Ab2GFDtq (ORCPT ); Thu, 5 Jul 2012 23:49:46 -0400 Received: by lbbgm6 with SMTP id gm6so14197786lbb.19 for ; Thu, 05 Jul 2012 20:49:44 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: From: Bjorn Helgaas Date: Thu, 5 Jul 2012 21:49:23 -0600 Message-ID: Subject: Re: 64 bit address to a pcie card To: Yinghai Lu Cc: sumit chaudhary , linux-pci@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-pci-owner@vger.kernel.org List-ID: On Thu, Jul 5, 2012 at 6:14 PM, Yinghai Lu wrote: > On Thu, Jul 5, 2012 at 8:16 AM, Bjorn Helgaas wrote: >> [Added back cc: linux-pci so others can help, too] >> >> What exactly is the problem? Is there a device that isn't working as expected? >> >> The device at 07:00.0 does indeed have 64-bit BARs, and they happen to >> be assigned addresses below 4GB: >> >> pci 0000:07:00.0: reg 10: [mem 0xfddff000-0xfddfffff 64bit] >> pci 0000:07:00.0: reg 18: [mem 0xbf000000-0xbfffffff 64bit pref] >> pci 0000:07:00.0: reg 20: [mem 0x40000000-0x7fffffff 64bit pref] >> >> This is perfectly normal. The fact that the BAR supports a full >> 64-bit address doesn't mean it has to be assigned space above 4GB. >> The BIOS assigned these addresses, and Linux found no reason to change >> them, so we just left them alone. > > The system only has 1G ram installed, and the card need 1G 64bit pref. > > Maybe BIOS could push that above 4G, if the system get 4G RAM installed. Maybe. I doubt it, because BIOS didn't report any host bridge apertures above 4GB. But I haven't heard about a problem yet. If there's no problem, there's no problem.