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 40BF4C433EF for ; Thu, 31 Mar 2022 20:11:20 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 501AB10E13B; Thu, 31 Mar 2022 20:11:19 +0000 (UTC) Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by gabe.freedesktop.org (Postfix) with ESMTPS id 1706F10E13B for ; Thu, 31 Mar 2022 20:11:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1648757478; x=1680293478; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=6FSUhXWHeTmhsQiYv8LR1T0P9fCp5kqXY7NGpeKWnqo=; b=JYfxVyTANePT9CZ/KLiAUJuOJ5SIPfHDbSML22f11Gn/m0ZF8PylxEUg odmvbNOfDYG5c2d2R65BooCXfTSgXLwjGOXyBSVqoAQemH76rWiTOF8pL cJfmCmzUYpvEuOEJZaC3QforHUCBoca8OtSaH9Rt2ANSFbvntssogNd/2 MqZB7Fyv2KBjRT16IS+cenhyJTT42ejVmqPSQTR1QL3Fcaa2iwiDf+zUi 6ioI7AZ0rPuqZDtCeh7MBLHgdbPaBLTxxXS/8f8KFTUhJRe0DdqDeuUhI 6Jmd/lGVzU8DZ2S2FPNqJ4KueEBWh5Jyrsiq+M9gpHPznSU5UHOYNK6xO w==; X-IronPort-AV: E=McAfee;i="6200,9189,10302"; a="257530394" X-IronPort-AV: E=Sophos;i="5.90,225,1643702400"; d="scan'208";a="257530394" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 Mar 2022 13:11:05 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.90,225,1643702400"; d="scan'208";a="695617698" Received: from stinkpipe.fi.intel.com (HELO stinkbox) ([10.237.72.61]) by fmsmga001.fm.intel.com with SMTP; 31 Mar 2022 13:11:01 -0700 Received: by stinkbox (sSMTP sendmail emulation); Thu, 31 Mar 2022 23:11:00 +0300 Date: Thu, 31 Mar 2022 23:11:00 +0300 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Daniel Vetter Subject: Re: [PATCH v4] drm/atomic-helpers: remove legacy_cursor_update hacks Message-ID: References: <20220331130545.625721-1-maxime@cerno.tech> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Patchwork-Hint: comment X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Dom Cobley , Tim Gover , Dave Stevenson , Daniel Vetter , Michel =?iso-8859-1?Q?D=E4nzer?= , dri-devel@lists.freedesktop.org, "Kazlauskas, Nicholas" , Maxime Ripard , Daniel Vetter , mikita.lipski@amd.com, Phil Elwell Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Thu, Mar 31, 2022 at 10:02:53PM +0200, Daniel Vetter wrote: > On Thu, Mar 31, 2022 at 10:52:54PM +0300, Ville Syrjälä wrote: > > On Thu, Mar 31, 2022 at 09:11:29PM +0200, Daniel Vetter wrote: > > > On Thu, Mar 31, 2022 at 06:48:43PM +0300, Ville Syrjälä wrote: > > > > On Thu, Mar 31, 2022 at 05:14:29PM +0200, Daniel Vetter wrote: > > > > > On Thu, Mar 31, 2022 at 04:25:13PM +0300, Ville Syrjälä wrote: > > > > > > On Thu, Mar 31, 2022 at 03:05:45PM +0200, Maxime Ripard wrote: > > > > > > > From: Daniel Vetter > > > > > > > > > > > > > > The stuff never really worked, and leads to lots of fun because it > > > > > > > out-of-order frees atomic states. Which upsets KASAN, among other > > > > > > > things. > > > > > > > > > > > > > > For async updates we now have a more solid solution with the > > > > > > > ->atomic_async_check and ->atomic_async_commit hooks. Support for that > > > > > > > for msm and vc4 landed. nouveau and i915 have their own commit > > > > > > > routines, doing something similar. > > > > > > > > > > > > > > For everyone else it's probably better to remove the use-after-free > > > > > > > bug, and encourage folks to use the async support instead. The > > > > > > > affected drivers which register a legacy cursor plane and don't either > > > > > > > use the new async stuff or their own commit routine are: amdgpu, > > > > > > > atmel, mediatek, qxl, rockchip, sti, sun4i, tegra, virtio, and vmwgfx. > > > > > > > > > > > > > > Inspired by an amdgpu bug report. > > > > > > > > > > > > > > v2: Drop RFC, I think with amdgpu converted over to use > > > > > > > atomic_async_check/commit done in > > > > > > > > > > > > > > commit 674e78acae0dfb4beb56132e41cbae5b60f7d662 > > > > > > > Author: Nicholas Kazlauskas > > > > > > > Date: Wed Dec 5 14:59:07 2018 -0500 > > > > > > > > > > > > > > drm/amd/display: Add fast path for cursor plane updates > > > > > > > > > > > > > > we don't have any driver anymore where we have userspace expecting > > > > > > > solid legacy cursor support _and_ they are using the atomic helpers in > > > > > > > their fully glory. So we can retire this. > > > > > > > > > > > > > > v3: Paper over msm and i915 regression. The complete_all is the only > > > > > > > thing missing afaict. > > > > > > > > > > > > > > v4: Rebased on recent kernel, added extra link for vc4 bug. > > > > > > > > > > > > > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=199425 > > > > > > > Link: https://lore.kernel.org/all/20220221134155.125447-9-maxime@cerno.tech/ > > > > > > > Cc: mikita.lipski@amd.com > > > > > > > Cc: Michel Dänzer > > > > > > > Cc: harry.wentland@amd.com > > > > > > > Cc: Rob Clark > > > > > > > Cc: "Kazlauskas, Nicholas" > > > > > > > Tested-by: Maxime Ripard > > > > > > > Signed-off-by: Daniel Vetter > > > > > > > Signed-off-by: Maxime Ripard > > > > > > > --- > > > > > > > drivers/gpu/drm/drm_atomic_helper.c | 13 ------------- > > > > > > > drivers/gpu/drm/i915/display/intel_display.c | 13 +++++++++++++ > > > > > > > drivers/gpu/drm/msm/msm_atomic.c | 2 ++ > > > > > > > 3 files changed, 15 insertions(+), 13 deletions(-) > > > > > > > > > > > > > > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c > > > > > > > index 9603193d2fa1..a2899af82b4a 100644 > > > > > > > --- a/drivers/gpu/drm/drm_atomic_helper.c > > > > > > > +++ b/drivers/gpu/drm/drm_atomic_helper.c > > > > > > > @@ -1498,13 +1498,6 @@ drm_atomic_helper_wait_for_vblanks(struct drm_device *dev, > > > > > > > int i, ret; > > > > > > > unsigned int crtc_mask = 0; > > > > > > > > > > > > > > - /* > > > > > > > - * Legacy cursor ioctls are completely unsynced, and userspace > > > > > > > - * relies on that (by doing tons of cursor updates). > > > > > > > - */ > > > > > > > - if (old_state->legacy_cursor_update) > > > > > > > - return; > > > > > > > - > > > > > > > for_each_oldnew_crtc_in_state(old_state, crtc, old_crtc_state, new_crtc_state, i) { > > > > > > > if (!new_crtc_state->active) > > > > > > > continue; > > > > > > > @@ -2135,12 +2128,6 @@ int drm_atomic_helper_setup_commit(struct drm_atomic_state *state, > > > > > > > continue; > > > > > > > } > > > > > > > > > > > > > > - /* Legacy cursor updates are fully unsynced. */ > > > > > > > - if (state->legacy_cursor_update) { > > > > > > > - complete_all(&commit->flip_done); > > > > > > > - continue; > > > > > > > - } > > > > > > > - > > > > > > > if (!new_crtc_state->event) { > > > > > > > commit->event = kzalloc(sizeof(*commit->event), > > > > > > > GFP_KERNEL); > > > > > > > diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c > > > > > > > index bf7ce684dd8e..bde32f5a33cb 100644 > > > > > > > --- a/drivers/gpu/drm/i915/display/intel_display.c > > > > > > > +++ b/drivers/gpu/drm/i915/display/intel_display.c > > > > > > > @@ -8855,6 +8855,19 @@ static int intel_atomic_commit(struct drm_device *dev, > > > > > > > state->base.legacy_cursor_update = false; > > > > > > > } > > > > > > > > > > > > > > + /* > > > > > > > + * FIXME: Cut over to (async) commit helpers instead of hand-rolling > > > > > > > + * everything. > > > > > > > + */ > > > > > > > > > > > > Intel cursors can't even do async updates so this is rather > > > > > > nonsensical. What we need is some kind of reasonable mailbox > > > > > > support. > > > > > > > > > > This is not the async plane update you're thinking of. i915 really should > > > > > switch over more to atomic helpers. > > > > > > > > The comment should be clarified then. As is I have no real idea > > > > what it's trying to say. > > > > > > Use drm_atomic_commit and only overwrite atomic_commit_tail. > > > > You mean drm_atomic_helper_commit() I suppose? > > > > > But I'm not > > > really clear why the comment isn't clear - i915 is the only driver not > > > using them, maybe should start to take a look when they're so unfamiliar > > > :-P > > > > There are a lot of problems with that: > > - no uapi/hw state split so if there's anything that looks > > at the state it's very likely going to get things wrong > > - it doesn't know anything about i915's own state objects > > - uses wrong workqueues > > > > Those are the ones that immediately came to mind when I looked > > at it. Probably I missed some others as well. > > Yeah and we could have fixed them in the shared code, and 5+ years ago I > even had patches, but i915 gem team had the idea they know better. That > part really needs to be fixed, and if that means redoing a bunch of > display work because display team didn't push back on gem team reinventing > all the wheels ... tough luck. > > I suggest you get started. I offered to do the hw/uapi split in the core. You refused it. I raised my objection to the introduction of the single lock scheme for private state objects. No one was interested. I don't think this situation is on me. -- Ville Syrjälä Intel