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 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 B3CF1C4741F for ; Mon, 9 Nov 2020 13:16:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 713352083B for ; Mon, 9 Nov 2020 13:16:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604927767; bh=XvjeH3eqI8qrSv4FQyYupaTcNbZkt1CBRAYb1VDSO6o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=HDSdFHDgRCZVIiw0v0EoOpP6LUcvznkuMyUMDa93ugpP0caa22RnrC+44+sYbHCyV Ib1c38i+EgCMOlMv2bfKgZJeB2tox1cTeOXsADQPQJO3R+PbXbehphg9wRE2G9lRk2 OT+ZFInX1hNKgMjVBpD69rPLIxyyCS2PECN6hITQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387440AbgKINQG (ORCPT ); Mon, 9 Nov 2020 08:16:06 -0500 Received: from mail.kernel.org ([198.145.29.99]:42960 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387420AbgKINQD (ORCPT ); Mon, 9 Nov 2020 08:16:03 -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 A3DE2208FE; Mon, 9 Nov 2020 13:16:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604927762; bh=XvjeH3eqI8qrSv4FQyYupaTcNbZkt1CBRAYb1VDSO6o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=LURNk0tXnloRlUJ+mVkdTDYm5smYRNs9ylXMiFrwtA9nYtUInFHxzRpiWCf6NSCO5 edcNb9Qw82kmokrTprYRWWW7dwQjXCXbmB0VjAQaiYOqf6M/jgEZK+3vHWWmSXeaFU jduQbRv1fFZwPGOcFTm1ktr+aKBU7HzFoOwMyCxE= 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 5.9 013/133] drm/i915/gt: Delay execlist processing for tgl Date: Mon, 9 Nov 2020 13:54:35 +0100 Message-Id: <20201109125031.358299349@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201109125030.706496283@linuxfoundation.org> References: <20201109125030.706496283@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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 @@ -2661,6 +2661,9 @@ static void process_csb(struct intel_eng smp_wmb(); /* complete the seqlock */ WRITE_ONCE(execlists->active, execlists->inflight); + /* XXX Magic delay for tgl */ + ENGINE_POSTING_READ(engine, RING_CONTEXT_STATUS_PTR); + WRITE_ONCE(execlists->pending[0], NULL); } else { if (GEM_WARN_ON(!*execlists->active)) {