Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754124AbbDHP1h (ORCPT ); Wed, 8 Apr 2015 11:27:37 -0400 Received: from mail.skyhub.de ([78.46.96.112]:60736 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753401AbbDHP1d (ORCPT ); Wed, 8 Apr 2015 11:27:33 -0400 Date: Wed, 8 Apr 2015 17:25:22 +0200 From: Borislav Petkov To: Aravind Gopalakrishnan Cc: mingo@redhat.com, bp@suse.de, linux-kernel@vger.kernel.org, Suravee.Suthikulpanit@amd.com, Joerg Rodel , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Bjorn Helgaas , x86-ml Subject: Re: [PATCH V2] x86/gart: Check for GART support before accessing GART registers Message-ID: <20150408152522.GH3611@pd.tnic> References: <1428443197-3834-1-git-send-email-Aravind.Gopalakrishnan@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1428443197-3834-1-git-send-email-Aravind.Gopalakrishnan@amd.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2561 Lines: 64 On Tue, Apr 07, 2015 at 04:46:37PM -0500, Aravind Gopalakrishnan wrote: > GART registers are not present in newer processors (Fam15h, Model 10h > and later). So, avoid accesses to GART registers in PCI config > space by returning early in early_gart_iommu_check() and > gart_iommu_hole_init() if GART is not available. > > Current code doesn't break on existing processors but there are some > side effects: > > We get bogus AGP aperture messages which are simply noise on > GART-less processors: > > AGP: Node 0: aperture [bus addr 0x00000000-0x01ffffff] (32MB) > AGP: Your BIOS doesn't leave aperture memory hole > AGP: Please enable the IOMMU option in the BIOS setup > AGP: This costs you 64MB of RAM > AGP: Mapping aperture over RAM [mem 0xd4000000-0xd7ffffff] > > We can avoid calling allocate_aperture() and would not have to > wastefully reserve 64MB of RAM with memblock_reserve(). Also, we can > avoid having to loop through all PCI buses and devices twice, searching > for a non-existent AGP bridge if we bail out early. > > Refactoring the family check used in amd_nb.c into an inline function > so we can use it here as well as in amd_nb.c > > Fix some typos while at it. > Tested the patch on Fam10h and Fam15h Model 00h-fh and this code > runs fine. On Fam15h Model 60h-6fh and on Fam16h, we bail early > as they don't have GART. > > Signed-off-by: Aravind Gopalakrishnan > Reviewed-by: Suravee Suthikulpanit > Cc: Joerg Rodel > Cc: Thomas Gleixner > Cc: Ingo Molnar > Cc: H. Peter Anvin > Cc: Bjorn Helgaas > Cc: x86-ml > --- > Changes in V2: > - move amd_gart_present() before any other checks as it's least intrusive (per Boris) > - fix typos in code and commit message (per Ingo) > - minor change to subject line (per Boris' change) > - Link to V1:http://marc.info/?l=linux-kernel&m=142792069809730&w=2 > > arch/x86/include/asm/amd_nb.h | 11 +++++++++++ > arch/x86/kernel/amd_nb.c | 4 +--- > arch/x86/kernel/aperture_64.c | 8 +++++++- > 3 files changed, 19 insertions(+), 4 deletions(-) Applied, thanks. -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. -- -- 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/