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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5518DC433F5 for ; Mon, 21 Mar 2022 12:22:51 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 589D410E274; Mon, 21 Mar 2022 12:22:46 +0000 (UTC) Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by gabe.freedesktop.org (Postfix) with ESMTPS id 228DA10E2D7; Mon, 21 Mar 2022 12:22:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1647865364; x=1679401364; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=CYTdcb5m08Vqi5v4XQvwqi2xu9a+DBIEtPO0UEoQ73E=; b=NoEMCWTFCZBQH0BD9nMLQaZ6I5MX86ZXUJ/3XWeZckD/oW9422KRbVRS thDm/xWo2C5rKW1Xg/hpTVvG/SYfoj3JCJdTeTCoJqisAywC2b5tJFuzE 7FldWqWHHM/Kxsz8RPbP+enhn1Ztxwu1oyh4SPyoCeWvHmH+N/FEjptk7 awK7FL3pmiQpXU+l2HulRpzoGXHh06RvSMuyehJIphDXKc/4l4AdB4q2S YjMGJgJ0mRt2uqi3CK1VylHj2o33g92n5sqp0Tw5N8A0qZdZAqBPwK6LD 2bn1GF2tAZYf5PLCEo5BlGUlCLqK4/XNlY6Iv/3Zm9hOtxomC8R9W9gkM w==; X-IronPort-AV: E=McAfee;i="6200,9189,10292"; a="256355015" X-IronPort-AV: E=Sophos;i="5.90,198,1643702400"; d="scan'208";a="256355015" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Mar 2022 05:22:43 -0700 X-IronPort-AV: E=Sophos;i="5.90,198,1643702400"; d="scan'208";a="559845676" Received: from atnordon-mobl1.ger.corp.intel.com (HELO [10.213.230.67]) ([10.213.230.67]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Mar 2022 05:22:40 -0700 Message-ID: Date: Mon, 21 Mar 2022 12:22:37 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Content-Language: en-US To: =?UTF-8?Q?Thomas_Hellstr=c3=b6m?= , Michael Cheng , intel-gfx@lists.freedesktop.org References: <20220319194227.297639-1-michael.cheng@intel.com> <4c86ae70-6f97-7a7c-1fd4-5e73ca29d0ba@linux.intel.com> <5db61477-6064-ada0-82a7-c1dc659dacad@linux.intel.com> From: Tvrtko Ursulin Organization: Intel Corporation UK Plc In-Reply-To: <5db61477-6064-ada0-82a7-c1dc659dacad@linux.intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Subject: Re: [Intel-gfx] [PATCH 0/4] Drop wbinvd_on_all_cpus usage X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: daniel.vetter@ffwll.ch, lucas.demarchi@intel.com, dri-devel@lists.freedesktop.org, chris@chris-wilson.co.uk, Matthew Auld Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On 21/03/2022 11:03, Thomas Hellström wrote: > Hi, Tvrtko. > > On 3/21/22 11:27, Tvrtko Ursulin wrote: >> >> On 19/03/2022 19:42, Michael Cheng wrote: >>> To align with the discussion in [1][2], this patch series drops all >>> usage of >>> wbvind_on_all_cpus within i915 by either replacing the call with certain >>> drm clflush helpers, or reverting to a previous logic. >> >> AFAIU, complaint from [1] was that it is wrong to provide non x86 >> implementations under the wbinvd_on_all_cpus name. Instead an arch >> agnostic helper which achieves the same effect could be created. Does >> Arm have such concept? > > I also understand Linus' email like we shouldn't leak incoherent IO to > other architectures, meaning any remaining wbinvd()s should be X86 only. The last part is completely obvious since it is a x86 instruction name. But I think we can't pick a solution until we know how the concept maps to Arm and that will also include seeing how the drm_clflush_sg for Arm would look. Is there a range based solution, or just a big hammer there. If the latter, then it is no good to churn all these reverts but instead an arch agnostic wrapper, with a generic name, would be the way to go. Regards, Tvrtko > Also, wbinvd_on_all_cpus() can become very costly, hence prefer the > range apis when possible if they can be verified not to degrade > performance. > > >> >> Given that the series seems to be taking a different route, avoiding >> the need to call wbinvd_on_all_cpus rather than what [1] suggests >> (note drm_clflush_sg can still call it!?), concern is that the series >> has a bunch of reverts and each one needs to be analyzed. > > > Agreed. > > /Thomas > > > >> >> For instance looking at just the last one, 64b95df91f44, who has >> looked at the locking consequences that commit describes: >> >> """ >>     Inside gtt_restore_mappings() we currently take the >> obj->resv->lock, but >>     in the future we need to avoid taking this fs-reclaim tainted lock >> as we >>     need to extend the coverage of the vm->mutex. Take advantage of the >>     single-threaded nature of the early resume phase, and do a single >>     wbinvd() to flush all the GTT objects en masse. >> >> """ >> >> ? >> >> Then there are suspend and freeze reverts which presumably can regress >> the suspend times. Any data on those? >> >> Adding Matt since he was the reviewer for that work so might remember >> something. >> >> Regards, >> >> Tvrtko >> >> >>> [1]. >>> https://lists.freedesktop.org/archives/dri-devel/2021-November/330928.html >>> >>> [2]. https://patchwork.freedesktop.org/patch/475752/?series=99991&rev=5 >>> >>> Michael Cheng (4): >>>    i915/gem: drop wbinvd_on_all_cpus usage >>>    Revert "drm/i915/gem: Almagamate clflushes on suspend" >>>    i915/gem: Revert i915_gem_freeze to previous logic >>>    drm/i915/gt: Revert ggtt_resume to previous logic >>> >>>   drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c |  9 +--- >>>   drivers/gpu/drm/i915/gem/i915_gem_pm.c     | 56 ++++++++++++++-------- >>>   drivers/gpu/drm/i915/gt/intel_ggtt.c       | 17 +++---- >>>   drivers/gpu/drm/i915/gt/intel_gtt.h        |  2 +- >>>   4 files changed, 46 insertions(+), 38 deletions(-) >>>