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=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 09192C433F5 for ; Wed, 22 Sep 2021 01:45:40 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id BB97660F44 for ; Wed, 22 Sep 2021 01:45:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org BB97660F44 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 3ABF16EA04; Wed, 22 Sep 2021 01:45:39 +0000 (UTC) Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) by gabe.freedesktop.org (Postfix) with ESMTPS id 5571E6EA04; Wed, 22 Sep 2021 01:45:38 +0000 (UTC) X-IronPort-AV: E=McAfee;i="6200,9189,10114"; a="284510103" X-IronPort-AV: E=Sophos;i="5.85,312,1624345200"; d="scan'208";a="284510103" Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Sep 2021 18:45:37 -0700 X-IronPort-AV: E=Sophos;i="5.85,312,1624345200"; d="scan'208";a="701973471" Received: from jons-linux-dev-box.fm.intel.com (HELO jons-linux-dev-box) ([10.1.27.20]) by fmsmga006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Sep 2021 18:45:37 -0700 Date: Tue, 21 Sep 2021 18:40:41 -0700 From: Matthew Brost To: Lucas De Marchi Cc: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Message-ID: <20210922014041.GA13907@jons-linux-dev-box> References: <20210921174332.30784-1-matthew.brost@intel.com> <20210921184637.ullcwswqd6z5hi4j@ldmartin-desk2> <20210921225514.GA8109@jons-linux-dev-box> <20210921232931.5j4h4l7tmfp7mjzj@ldmartin-desk2> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210921232931.5j4h4l7tmfp7mjzj@ldmartin-desk2> User-Agent: Mutt/1.9.4 (2018-02-28) Subject: Re: [Intel-gfx] [PATCH] drm/i915: fix blank screen booting crashes 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: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Tue, Sep 21, 2021 at 04:29:31PM -0700, Lucas De Marchi wrote: > On Tue, Sep 21, 2021 at 03:55:15PM -0700, Matthew Brost wrote: > > On Tue, Sep 21, 2021 at 11:46:37AM -0700, Lucas De Marchi wrote: > > > On Tue, Sep 21, 2021 at 10:43:32AM -0700, Matthew Brost wrote: > > > > From: Hugh Dickins > > > > > > > > 5.15-rc1 crashes with blank screen when booting up on two ThinkPads > > > > using i915. Bisections converge convincingly, but arrive at different > > > > and surprising "culprits", none of them the actual culprit. > > > > > > > > netconsole (with init_netconsole() hacked to call i915_init() when > > > > logging has started, instead of by module_init()) tells the story: > > > > > > > > kernel BUG at drivers/gpu/drm/i915/i915_sw_fence.c:245! > > > > with RSI: ffffffff814d408b pointing to sw_fence_dummy_notify(). > > > > I've been building with CONFIG_CC_OPTIMIZE_FOR_SIZE=y, and that > > > > function needs to be 4-byte aligned. > > > > > > > > v2: > > > > (Jani Nikula) > > > > - Change BUG_ON to WARN_ON > > > > v3: > > > > (Jani / Tvrtko) > > > > - Short circuit __i915_sw_fence_init on WARN_ON > > > > > > > > Fixes: 62eaf0ae217d ("drm/i915/guc: Support request cancellation") > > > > Signed-off-by: Hugh Dickins > > > > Signed-off-by: Matthew Brost > > > > Reviewed-by: Matthew Brost > > > > --- > > > > drivers/gpu/drm/i915/gt/intel_context.c | 4 ++-- > > > > drivers/gpu/drm/i915/i915_sw_fence.c | 17 ++++++++++------- > > > > 2 files changed, 12 insertions(+), 9 deletions(-) > > > > > > > > diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c > > > > index ff637147b1a9..e7f78bc7ebfc 100644 > > > > --- a/drivers/gpu/drm/i915/gt/intel_context.c > > > > +++ b/drivers/gpu/drm/i915/gt/intel_context.c > > > > @@ -362,8 +362,8 @@ static int __intel_context_active(struct i915_active *active) > > > > return 0; > > > > } > > > > > > > > > > > -static int sw_fence_dummy_notify(struct i915_sw_fence *sf, > > > > - enum i915_sw_fence_notify state) > > > > +static int __i915_sw_fence_call > > > > +sw_fence_dummy_notify(struct i915_sw_fence *sf, enum i915_sw_fence_notify state) > > > > { > > > > return NOTIFY_DONE; > > > > } > > > > diff --git a/drivers/gpu/drm/i915/i915_sw_fence.c b/drivers/gpu/drm/i915/i915_sw_fence.c > > > > index c589a681da77..08cea73264e7 100644 > > > > --- a/drivers/gpu/drm/i915/i915_sw_fence.c > > > > +++ b/drivers/gpu/drm/i915/i915_sw_fence.c > > > > @@ -13,9 +13,9 @@ > > > > #include "i915_selftest.h" > > > > > > > > #if IS_ENABLED(CONFIG_DRM_I915_DEBUG) > > > > -#define I915_SW_FENCE_BUG_ON(expr) BUG_ON(expr) > > > > +#define I915_SW_FENCE_WARN_ON(expr) WARN_ON(expr) > > > > #else > > > > -#define I915_SW_FENCE_BUG_ON(expr) BUILD_BUG_ON_INVALID(expr) > > > > +#define I915_SW_FENCE_WARN_ON(expr) BUILD_BUG_ON_INVALID(expr) > > > > #endif > > > > > > > > static DEFINE_SPINLOCK(i915_sw_fence_lock); > > > > @@ -129,7 +129,10 @@ static int __i915_sw_fence_notify(struct i915_sw_fence *fence, > > > > i915_sw_fence_notify_t fn; > > > > > > > > fn = (i915_sw_fence_notify_t)(fence->flags & I915_SW_FENCE_MASK); > > > > - return fn(fence, state); > > > > + if (likely(fn)) > > > > + return fn(fence, state); > > > > + else > > > > + return 0; > > > > > > since the knowledge for these being NULL (or with the wrong alignment) > > > are in the init/reinit functions, wouldn't it be better to just add a > > > fence_nop() and assign it there instead this likely() here? > > > > > > > Maybe? I prefer the way it is. > > > > > > } > > > > > > > > #ifdef CONFIG_DRM_I915_SW_FENCE_DEBUG_OBJECTS > > > > @@ -242,9 +245,9 @@ void __i915_sw_fence_init(struct i915_sw_fence *fence, > > > > const char *name, > > > > struct lock_class_key *key) > > > > { > > > > - BUG_ON(!fn || (unsigned long)fn & ~I915_SW_FENCE_MASK); > > > > - > > > > __init_waitqueue_head(&fence->wait, name, key); > > > > + if (WARN_ON(!fn || (unsigned long)fn & ~I915_SW_FENCE_MASK)) > > > > + return; > > > > > > like: > > > if (WARN_ON(!fn || (unsigned long)fn & ~I915_SW_FENCE_MASK)) > > > fence->flags = (unsigned long)sw_fence_dummy_notify; > > > else > > > fence->flags = (unsigned long)fn; > > > > > > > > > f you return here instead of calling i915_sw_fence_reinit(), aren't you > > > just going to use uninitialized memory later? At least in the selftests, > > > which allocate it with kmalloc()... I didn't check others. > > > > > > > I don't think so, maybe the fence won't work but it won't blow up > > either. > > > > > > > > For the bug fix we could just add the __aligned(4) and leave the rest to a > > > separate patch. > > > > > > > The bug was sw_fence_dummy_notify in gt/intel_context.c was not 4 byte > > align which triggered a BUG_ON during boot which blank screened a > > laptop. Jani / Tvrtko suggested that we make the BUG_ON to WARN_ONs so > > if someone makes this mistake in the future kernel should boot albiet > > with a WARNING. > > yes, I understood. But afaics with WARN_ON you are allowing it to > continue and may be using uninitialized memory later, just causing other > problems down the line, which may be equally difficult to debug. > > what I suggested is that there is the easy fix to apply to the current > rcX kernel, adding __aligned(4) to sw_fence_dummy_notify() (patch 1). > And there is the additional protection being added here (patch 2) which > is subject to the debate. > Got it. Will post as 2 different patches. > > > > The long term fix is just pull out the I915_SW_FENCE_MASK (stealing bits > > from a poitner) and we don't have to worry any of this. > > Patch 2 may not even be needed if you're going that route. But we are > not only protecting against unaligned, but also from code calling > i915_sw_fence_init() with a NULL fn. > Maybe, I'll just do the proper fix in patch #2 right away. Matt > Lucas De Marchi > > > > > Matt > > > > > > > > Lucas De Marchi > > > > > > > fence->flags = (unsigned long)fn; > > > > > > > > i915_sw_fence_reinit(fence); > > > > @@ -257,8 +260,8 @@ void i915_sw_fence_reinit(struct i915_sw_fence *fence) > > > > atomic_set(&fence->pending, 1); > > > > fence->error = 0; > > > > > > > > - I915_SW_FENCE_BUG_ON(!fence->flags); > > > > - I915_SW_FENCE_BUG_ON(!list_empty(&fence->wait.head)); > > > > + I915_SW_FENCE_WARN_ON(!fence->flags); > > > > + I915_SW_FENCE_WARN_ON(!list_empty(&fence->wait.head)); > > > > } > > > > > > > > void i915_sw_fence_commit(struct i915_sw_fence *fence) > > > > -- > > > > 2.32.0 > > > >