From patchwork Mon Nov 9 12:54:59 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 322660 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 05493C2D0A3 for ; Mon, 9 Nov 2020 13:29:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9B931206ED for ; Mon, 9 Nov 2020 13:29:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604928569; bh=BjGt8GDopeSM3gZ1nWWAZcXAqLRJr+0iISeU1sQ3PU8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=TZeEJ2nquTEGpHEzKRlVXZRk5dGhx6Fo1WaQUB6vlDb+0mkJxdM0TzdaDZfwJZaQZ ukkI1sTyLpx0wLSBDI4xJKsstysPHYplBTTKckq/rEHhnKaESdOwXFp3di34u4yaWb XWZka4ogRdI/gU0Np/f7PeXhYOpTnArInsNQN2Hw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732582AbgKINMX (ORCPT ); Mon, 9 Nov 2020 08:12:23 -0500 Received: from mail.kernel.org ([198.145.29.99]:37756 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732546AbgKINML (ORCPT ); Mon, 9 Nov 2020 08:12:11 -0500 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 01C1E2076E; Mon, 9 Nov 2020 13:12:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604927530; bh=BjGt8GDopeSM3gZ1nWWAZcXAqLRJr+0iISeU1sQ3PU8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=juGzCVl8qIxGDiklQ/AqW5XHgA1bNIOodFspjXGMR4cvakMZllWFul4JiQvqoRpYA /0XyPsgeB9uFcB4VIooKaCUhCCrXzAVm453frQYrlOZifsYMBa48Ue+MyYUXBUKPL9 EogA9kB/+lCXFiHTLfgzpIh5mPqib1rMZERM12Rw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Chris Wilson , Mika Kuoppala , Bruce Chang , Joonas Lahtinen , Rodrigo Vivi Subject: [PATCH 5.4 02/85] drm/i915/gt: Delay execlist processing for tgl Date: Mon, 9 Nov 2020 13:54:59 +0100 Message-Id: <20201109125022.735129144@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201109125022.614792961@linuxfoundation.org> References: <20201109125022.614792961@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Chris Wilson commit 9b99e5ba3e5d68039bd6b657e4bbe520a3521f4c upstream. When running gem_exec_nop, it floods the system with many requests (with the goal of userspace submitting faster than the HW can process a single empty batch). This causes the driver to continually resubmit new requests onto the end of an active context, a flood of lite-restore preemptions. If we time this just right, Tigerlake hangs. Inserting a small delay between the processing of CS events and submitting the next context, prevents the hang. Naturally it does not occur with debugging enabled. The suspicion then is that this is related to the issues with the CS event buffer, and inserting an mmio read of the CS pointer status appears to be very successful in preventing the hang. Other registers, or uncached reads, or plain mb, do not prevent the hang, suggesting that register is key -- but that the hang can be prevented by a simple udelay, suggests it is just a timing issue like that encountered by commit 233c1ae3c83f ("drm/i915/gt: Wait for CSB entries on Tigerlake"). Also note that the hang is not prevented by applying CTX_DESC_FORCE_RESTORE, or by inserting a delay on the GPU between requests. Signed-off-by: Chris Wilson Cc: Mika Kuoppala Cc: Bruce Chang Cc: Joonas Lahtinen Cc: stable@vger.kernel.org Acked-by: Mika Kuoppala Link: https://patchwork.freedesktop.org/patch/msgid/20201015195023.32346-1-chris@chris-wilson.co.uk (cherry picked from commit 6ca7217dffaf1abba91558e67a2efb655ac91405) Signed-off-by: Rodrigo Vivi Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/i915/gt/intel_lrc.c | 3 +++ 1 file changed, 3 insertions(+) --- a/drivers/gpu/drm/i915/gt/intel_lrc.c +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c @@ -1574,6 +1574,9 @@ static void process_csb(struct intel_eng if (!inject_preempt_hang(execlists)) ring_set_paused(engine, 0); + /* XXX Magic delay for tgl */ + ENGINE_POSTING_READ(engine, RING_CONTEXT_STATUS_PTR); + WRITE_ONCE(execlists->pending[0], NULL); break;