From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 181CBC6FD1D for ; Fri, 17 Mar 2023 12:58:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230486AbjCQM6r (ORCPT ); Fri, 17 Mar 2023 08:58:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40784 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230474AbjCQM6q (ORCPT ); Fri, 17 Mar 2023 08:58:46 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6BCBC769C for ; Fri, 17 Mar 2023 05:58:44 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 072B262298 for ; Fri, 17 Mar 2023 12:58:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 11D41C433D2; Fri, 17 Mar 2023 12:58:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1679057923; bh=9fkR36fLv6f0kVwvUKUx5iu1I+qJ6ceMvK9paF9H+HA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=MMC+dsP+Ufrlzba2r6GPhpDUUvBUZJwiOoDBkiWRIz9zruB3T75aa80eiE/9zdnhE o1DX2PN3Fmuzuvpdpwidum8UCg7QiWhnc/uQO7Pm8nX7eebK+L/WE6I4helDViZqaa 7VICf04DHalKaD30xdt/MigO+/+ULwbaY2+YINoQ= Date: Fri, 17 Mar 2023 13:58:41 +0100 From: Greg KH To: John Harrison Cc: stable@vger.kernel.org, Joonas Lahtinen , Jani Nikula , Rodrigo Vivi , Tvrtko Ursulin , intel-gfx@lists.freedesktop.org, Jouni =?iso-8859-1?Q?H=F6gander?= , Daniele Ceraolo Spurio , Jani Nikula Subject: Re: [PATCH 5.4.y] drm/i915: Don't use BAR mappings for ring buffers with LLC Message-ID: References: <167820543971229@kroah.com> <20230314022211.1393031-1-John.C.Harrison@Intel.com> <5ed286b7-c2df-9e63-d85a-be9994f93eec@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5ed286b7-c2df-9e63-d85a-be9994f93eec@intel.com> Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Thu, Mar 16, 2023 at 01:58:35PM -0700, John Harrison wrote: > On 3/15/2023 10:57, Greg KH wrote: > > On Wed, Mar 15, 2023 at 10:07:53AM -0700, John Harrison wrote: > > > On 3/15/2023 00:51, Greg KH wrote: > > > > On Mon, Mar 13, 2023 at 07:22:11PM -0700, John.C.Harrison@Intel.com wrote: > > > > > From: John Harrison > > > > > > > > > > Direction from hardware is that ring buffers should never be mapped > > > > > via the BAR on systems with LLC. There are too many caching pitfalls > > > > > due to the way BAR accesses are routed. So it is safest to just not > > > > > use it. > > > > > > > > > > Signed-off-by: John Harrison > > > > > Fixes: 9d80841ea4c9 ("drm/i915: Allow ringbuffers to be bound anywhere") > > > > > Cc: Chris Wilson > > > > > Cc: Joonas Lahtinen > > > > > Cc: Jani Nikula > > > > > Cc: Rodrigo Vivi > > > > > Cc: Tvrtko Ursulin > > > > > Cc: intel-gfx@lists.freedesktop.org > > > > > Cc: # v4.9+ > > > > > Tested-by: Jouni Högander > > > > > Reviewed-by: Daniele Ceraolo Spurio > > > > > Link: https://patchwork.freedesktop.org/patch/msgid/20230216011101.1909009-3-John.C.Harrison@Intel.com > > > > > (cherry picked from commit 65c08339db1ada87afd6cfe7db8e60bb4851d919) > > > > > Signed-off-by: Jani Nikula > > > > > (cherry picked from commit 85636167e3206c3fbd52254fc432991cc4e90194) > > > > > Signed-off-by: John Harrison > > > > > --- > > > > > drivers/gpu/drm/i915/gt/intel_ringbuffer.c | 4 ++-- > > > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > Also queued up for 5.10.y, you forgot that one :) > > > I'm still working through the backlog of them. > > > > > > Note that these patches must all be applied as a pair. The 'don't use > > > stolen' can be applied in isolation but won't totally fix the problem. > > > However, applying 'don't use BAR mappings' without applying the stolen patch > > > first will results in problems such as the failure to boot that was recently > > > reported and resulted in a revert in one of the trees. > > I do not understand, you only submitted 1 patch here, what is the > > "pair"? > The original patch series was two patches - > https://patchwork.freedesktop.org/series/114080/. One to not use stolen > memory and the other to not use BAR mappings. If the anti-BAR patch is > applied without the anti-stolen patch then the i915 driver will attempt to > access stolen memory directly which will fail. So both patches must be > applied and in the correct order to fix the problem of cache aliasing when > using BAR accesses on LLC systems. > > As above, I am working my way through the bunch of 'FAILED patch' emails. > The what-to-do instructions in those emails explicitly say to send the patch > individually in reply to the 'FAILED' message rather than as part of any > original series. So what commits exactly in Linus's tree should be in these stable branches? Sorry, I still do not understand if we are missing one or if we need to revert something. confused, greg k-h