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=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,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 E9B01C433E6 for ; Mon, 4 Jan 2021 16:07:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BF91A21D93 for ; Mon, 4 Jan 2021 16:07:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729322AbhADQHG (ORCPT ); Mon, 4 Jan 2021 11:07:06 -0500 Received: from mail.kernel.org ([198.145.29.99]:39930 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728868AbhADQCh (ORCPT ); Mon, 4 Jan 2021 11:02:37 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 9A9B9224D2; Mon, 4 Jan 2021 16:01:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1609776116; bh=kbXVDURpVO4n7IDAFIoO6qDrcqygc9gNZYFaaVWklug=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lFtL3uPmD4C3SQbnOdYUnfyX0j9Uj1mCQG2kUVx52i1fLst7NvanZ6bTaYaP5s6lI Y72UB7CFt3DQVf+ZsDe5tWeqZaM349hJoahlxd70rax7HC9yIZdx6lIz+2Rg3MuXkH 84vwWmI4FdIK9feDlx/C38m2dyrRdbgbGnyzIEHc= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tomi Valkeinen , Thomas Zimmermann , Sam Ravnborg , Jiri Slaby , Bartlomiej Zolnierkiewicz , Linus Torvalds , Ben Skeggs , nouveau@lists.freedesktop.org, Daniel Vetter , "Gustavo A. R. Silva" , Tetsuo Handa , Peilin Ye , George Kennedy , Nathan Chancellor , Peter Rosin , Daniel Vetter Subject: [PATCH 5.10 28/63] fbcon: Disable accelerated scrolling Date: Mon, 4 Jan 2021 16:57:21 +0100 Message-Id: <20210104155710.187945647@linuxfoundation.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210104155708.800470590@linuxfoundation.org> References: <20210104155708.800470590@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: Daniel Vetter commit 39aead8373b3c20bb5965c024dfb51a94e526151 upstream. So ever since syzbot discovered fbcon, we have solid proof that it's full of bugs. And often the solution is to just delete code and remove features, e.g. 50145474f6ef ("fbcon: remove soft scrollback code"). Now the problem is that most modern-ish drivers really only treat fbcon as an dumb kernel console until userspace takes over, and Oops printer for some emergencies. Looking at drm drivers and the basic vesa/efi fbdev drivers shows that only 3 drivers support any kind of acceleration: - nouveau, seems to be enabled by default - omapdrm, when a DMM remapper exists using remapper rewriting for y/xpanning - gma500, but that is getting deleted now for the GTT remapper trick, and the accelerated copyarea never set the FBINFO_HWACCEL_COPYAREA flag, so unused (and could be deleted already I think). No other driver supportes accelerated fbcon. And fbcon is the only user of this accel code (it's not exposed as uapi through ioctls), which means we could garbage collect fairly enormous amounts of code if we kill this. Plus because syzbot only runs on virtual hardware, and none of the drivers for that have acceleration, we'd remove a huge gap in testing. And there's no other even remotely comprehensive testing aside from syzbot. This patch here just disables the acceleration code by always redrawing when scrolling. The plan is that once this has been merged for well over a year in released kernels, we can start to go around and delete a lot of code. v2: - Drop a few more unused local variables, somehow I missed the compiler warnings (Sam) - Fix typo in comment (Jiri) - add a todo entry for the cleanup (Thomas) v3: Remove more unused variables (0day) Reviewed-by: Tomi Valkeinen Reviewed-by: Thomas Zimmermann Reviewed-by: Greg Kroah-Hartman Acked-by: Sam Ravnborg Cc: Jiri Slaby Cc: Bartlomiej Zolnierkiewicz Cc: Greg Kroah-Hartman Cc: Linus Torvalds Cc: Ben Skeggs Cc: nouveau@lists.freedesktop.org Cc: Tomi Valkeinen Cc: Daniel Vetter Cc: Jiri Slaby Cc: "Gustavo A. R. Silva" Cc: Tetsuo Handa Cc: Peilin Ye Cc: George Kennedy Cc: Nathan Chancellor Cc: Peter Rosin Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20201029132229.4068359-1-daniel.vetter@ffwll.ch Signed-off-by: Greg Kroah-Hartman --- Documentation/gpu/todo.rst | 18 +++++++++++++++ drivers/video/fbdev/core/fbcon.c | 45 ++++++--------------------------------- 2 files changed, 26 insertions(+), 37 deletions(-) --- a/Documentation/gpu/todo.rst +++ b/Documentation/gpu/todo.rst @@ -273,6 +273,24 @@ Contact: Daniel Vetter, Noralf Tronnes Level: Advanced +Garbage collect fbdev scrolling acceleration +-------------------------------------------- + +Scroll acceleration is disabled in fbcon by hard-wiring p->scrollmode = +SCROLL_REDRAW. There's a ton of code this will allow us to remove: +- lots of code in fbcon.c +- a bunch of the hooks in fbcon_ops, maybe the remaining hooks could be called + directly instead of the function table (with a switch on p->rotate) +- fb_copyarea is unused after this, and can be deleted from all drivers + +Note that not all acceleration code can be deleted, since clearing and cursor +support is still accelerated, which might be good candidates for further +deletion projects. + +Contact: Daniel Vetter + +Level: Intermediate + idr_init_base() --------------- --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -1033,7 +1033,7 @@ static void fbcon_init(struct vc_data *v struct vc_data *svc = *default_mode; struct fbcon_display *t, *p = &fb_display[vc->vc_num]; int logo = 1, new_rows, new_cols, rows, cols, charcnt = 256; - int cap, ret; + int ret; if (WARN_ON(info_idx == -1)) return; @@ -1042,7 +1042,6 @@ static void fbcon_init(struct vc_data *v con2fb_map[vc->vc_num] = info_idx; info = registered_fb[con2fb_map[vc->vc_num]]; - cap = info->flags; if (logo_shown < 0 && console_loglevel <= CONSOLE_LOGLEVEL_QUIET) logo_shown = FBCON_LOGO_DONTSHOW; @@ -1147,11 +1146,13 @@ static void fbcon_init(struct vc_data *v ops->graphics = 0; - if ((cap & FBINFO_HWACCEL_COPYAREA) && - !(cap & FBINFO_HWACCEL_DISABLED)) - p->scrollmode = SCROLL_MOVE; - else /* default to something safe */ - p->scrollmode = SCROLL_REDRAW; + /* + * No more hw acceleration for fbcon. + * + * FIXME: Garbage collect all the now dead code after sufficient time + * has passed. + */ + p->scrollmode = SCROLL_REDRAW; /* * ++guenther: console.c:vc_allocate() relies on initializing @@ -1961,45 +1962,15 @@ static void updatescrollmode(struct fbco { struct fbcon_ops *ops = info->fbcon_par; int fh = vc->vc_font.height; - int cap = info->flags; - u16 t = 0; - int ypan = FBCON_SWAP(ops->rotate, info->fix.ypanstep, - info->fix.xpanstep); - int ywrap = FBCON_SWAP(ops->rotate, info->fix.ywrapstep, t); int yres = FBCON_SWAP(ops->rotate, info->var.yres, info->var.xres); int vyres = FBCON_SWAP(ops->rotate, info->var.yres_virtual, info->var.xres_virtual); - int good_pan = (cap & FBINFO_HWACCEL_YPAN) && - divides(ypan, vc->vc_font.height) && vyres > yres; - int good_wrap = (cap & FBINFO_HWACCEL_YWRAP) && - divides(ywrap, vc->vc_font.height) && - divides(vc->vc_font.height, vyres) && - divides(vc->vc_font.height, yres); - int reading_fast = cap & FBINFO_READS_FAST; - int fast_copyarea = (cap & FBINFO_HWACCEL_COPYAREA) && - !(cap & FBINFO_HWACCEL_DISABLED); - int fast_imageblit = (cap & FBINFO_HWACCEL_IMAGEBLIT) && - !(cap & FBINFO_HWACCEL_DISABLED); p->vrows = vyres/fh; if (yres > (fh * (vc->vc_rows + 1))) p->vrows -= (yres - (fh * vc->vc_rows)) / fh; if ((yres % fh) && (vyres % fh < yres % fh)) p->vrows--; - - if (good_wrap || good_pan) { - if (reading_fast || fast_copyarea) - p->scrollmode = good_wrap ? - SCROLL_WRAP_MOVE : SCROLL_PAN_MOVE; - else - p->scrollmode = good_wrap ? SCROLL_REDRAW : - SCROLL_PAN_REDRAW; - } else { - if (reading_fast || (fast_copyarea && !fast_imageblit)) - p->scrollmode = SCROLL_MOVE; - else - p->scrollmode = SCROLL_REDRAW; - } } #define PITCH(w) (((w) + 7) >> 3)