Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932321AbaKMLUa (ORCPT ); Thu, 13 Nov 2014 06:20:30 -0500 Received: from mail.skyhub.de ([78.46.96.112]:55880 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932396AbaKMLUY (ORCPT ); Thu, 13 Nov 2014 06:20:24 -0500 Date: Thu, 13 Nov 2014 12:20:17 +0100 From: Borislav Petkov To: Andy Lutomirski Cc: Ross Zwisler , linux-kernel@vger.kernel.org, H Peter Anvin , Ingo Molnar , Thomas Gleixner , David Airlie , dri-devel@lists.freedesktop.org, x86@kernel.org Subject: Re: [PATCH 6/6] x86: Use clwb in drm_clflush_virt_range Message-ID: <20141113112017.GA14416@pd.tnic> References: <1415731396-19364-1-git-send-email-ross.zwisler@linux.intel.com> <1415731396-19364-7-git-send-email-ross.zwisler@linux.intel.com> <5464220D.6090204@amacapital.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <5464220D.6090204@amacapital.net> 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 On Wed, Nov 12, 2014 at 07:14:21PM -0800, Andy Lutomirski wrote: > On 11/11/2014 10:43 AM, Ross Zwisler wrote: > > If clwb is available on the system, use it in drm_clflush_virt_range. > > If clwb is not available, fall back to clflushopt if you can. > > If clflushopt is not supported, fall all the way back to clflush. > > I don't know exactly what drm_clflush_virt_range (and the other > functions you're modifying similarly) are for, but it seems plausible to > me that they're used before reads to make sure that non-coherent memory > sees updated data. If that's true, then this will break it. Why would it break it? The updated cachelines will be in memory and subsequent reads will be serviced from the cache instead from going to memory as it is not invalidated as it would be by CLFLUSH. /me is puzzled. -- Regards/Gruss, Boris. Sent from a fat crate under my desk. Formatting is fine. -- -- 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/