Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752400Ab3FWUaK (ORCPT ); Sun, 23 Jun 2013 16:30:10 -0400 Received: from mail-la0-f51.google.com ([209.85.215.51]:55783 "EHLO mail-la0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751100Ab3FWUaI (ORCPT ); Sun, 23 Jun 2013 16:30:08 -0400 MIME-Version: 1.0 In-Reply-To: <51C75465.9060007@zytor.com> References: <51C3DDFA.7050204@zytor.com> <51C69732.1010906@gmail.com> <20130623192936.GA28655@khazad-dum.debian.net> <51C75465.9060007@zytor.com> Date: Mon, 24 Jun 2013 06:30:05 +1000 Message-ID: Subject: Re: MTRR use in drivers From: Dave Airlie To: "H. Peter Anvin" Cc: Henrique de Moraes Holschuh , Brice Goglin , Linux Kernel Mailing List , David Airlie , dri-devel@lists.freedesktop.org, Andy Lutomirski Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1713 Lines: 42 >>> Why do you care about performance when PAT is disabled? breaking old boxes just because, is just going to get reverted when I get the first regression report that you broke old boxes. Andy Lutomirski just submitted a bunch of patches to clean up the DRM usage of mtrrs, they are in drm-next, afaik we no longer add them on PAT systems. Dave. >> >> It will regress already slow boxes. We blacklist a LOT of P4s, PMs, etc and >> nobody ever took the pain to track down which ones of those actually have >> PAT+MTRR aliasing bugs. >> >> These boxes have boards like the Radeon X300, which needs either PAT or MTRR >> to not become unusable... >> > > We're talking hardware which is now many years old, but this is causing > very serious problems on real, modern hardware. As far as I understand > it, too, the blacklisting was precautionary (the only bug that I > personally know about is a performance bug, where WC would be > incorrectly converted to UC.) > > We need a way forward here. If it is the only way I think we would have > to sacrifice the old machines, but perhaps something can be worked out > (e.g. if PAT is disabled, fall back to MTRRs if available for ioremap_wc()). > > -hpa > > -- > 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/ -- 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/