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Date:   Wed, 23 May 2018 02:49:19 -0700
From:   Vito Caputo <vcaputo@pengaru.com>
To:     linux-kernel <linux-kernel@vger.kernel.org>
Cc:     ville.syrjala@linux.intel.com, daniel.vetter@ffwll.ch
Subject: Re: [REGRESSION] v4.17-rc4: xgalaga fails to start in fullscreen
 (default) mode
Message-ID: <20180523094919.s47ldq33hhbnodu2@shells.gnugeneration.com>
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 <20180521215718.7zwhhdanpnibp6la@shells.gnugeneration.com>
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On Mon, May 21, 2018 at 02:57:18PM -0700, Vito Caputo wrote:
> On Mon, May 21, 2018 at 12:53:20PM -0700, Vito Caputo wrote:
> > Hello all,
> > 
> > 4.17-rc4 (my latest kernel ATM) consistently fails to start xgalaga
> > without -window.  I will try find time to build the latest rc this
> > evening.
> > 
> > > ~$ xgalaga
> > > X Error of failed request:  BadValue (integer parameter out of range for operation)
> > >   Major opcode of failed request:  152 (XFree86-VidModeExtension)
> > >   Minor opcode of failed request:  10 (XF86VidModeSwitchToMode)
> > >   Value in failed request:  0x120004e
> > >   Serial number of failed request:  199
> > >   Current serial number in output stream:  203
> > 
> > Haven't dug into this much yet, only did a perfunctory check by booting into a
> > few older kernels (4.11, 4.12, 4.16) and the problem is absent on all of them.
> > It appears to be a 4.17-specific regression right now.
> > 
> > Also observed, though this is surely a different regression, the game
> > ran like molasses with -window, showing some prominent kworkers in top:
> > 
> >   692 vc        20   0  312852  45884  20556 R  32.0  1.2   0:08.69 Xorg           
> >   102 root      20   0       0      0      0 R  11.2  0.0   0:01.43 kworker/1:3    
> >    94 root      20   0       0      0      0 I   8.9  0.0   0:00.83 kworker/0:2    
> >   696 vc        20   0   39948   4124   2912 S   1.0  0.1   0:05.57 vwm            
> >   902 vc        30  10   46372   4144   3500 S   0.7  0.1   0:00.08 xgalaga        
> >   891 vc        30  10   44924   3868   3156 R   0.3  0.1   0:00.09 top            
> >   903 vc        30  10    4180   1184   1100 S   0.3  0.0   0:00.01 xgal.sndsrv.oss
> > 
> > The windowed performance issue was observed on the older kernels tested
> > as well, though 4.11 felt better and didn't have the busy kworkers.
> > 
> > I have not attempted to play xgalaga for ages, but it used to be perfectly
> > playable on this machine in windowed mode when I last did.
> > 
> > Machine is the venerable Thinkpad X61s, 1.8Ghz, Debian 9, config attached.
> > 
> 
> Just built and booted v4.17-rc6, still broken.

Bisected to:

e995ca0b8139c5f6807095464e969931b443f55a is the first bad commit
commit e995ca0b8139c5f6807095464e969931b443f55a
Author: Ville Syrj?l? <ville.syrjala@linux.intel.com>
Date:   Tue Nov 14 20:32:58 2017 +0200

    drm/i915: Provide a device level .mode_valid() hook
    
    We never support certain mode flags etc. Reject those early on in the
    mode_config.mode_valid() hook. That allows us to remove some duplicated
    checks from the connector .mode_valid() hooks, and it guarantees that
    we never see those flags even from user mode as the
    mode_config.mode_valid() hooks gets executed for those as well.
    
    Signed-off-by: Ville Syrj?l? <ville.syrjala@linux.intel.com>
    Link: https://patchwork.freedesktop.org/patch/msgid/20171114183258.16976-11-ville.syrjala@linux.intel.com
    Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Will CC Ville and Daniel.

Regards,
Vito Caputo