linux-kernel - Re: Thinkpad X1 Carbon 3rd - Reducing the compressed framebuffer size

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20180213174341.abcjlfjymxbcz25t@pali>
Date:   Tue, 13 Feb 2018 18:43:41 +0100
From:   Pali Rohár <pali.rohar@...il.com>
To:     Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc:     Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Airlie <airlied@...ux.ie>,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: Thinkpad X1 Carbon 3rd - Reducing the compressed framebuffer size

On Tuesday 13 February 2018 18:12:21 Ville Syrjälä wrote:
> On Tue, Feb 13, 2018 at 05:04:37PM +0100, Pali Rohár wrote:
> > $ cat /sys/kernel/debug/dri/0/i915_gem_stolen
> > Stolen:
> >    ffff8b55bf17e080:    g        16KiB 40 40 [ 0 0 0 0 ] 0  LLC dirty (pinned x 1) (ggtt offset: 00083000, size: 00004000, type: 0) (stolen: 00001000)
> >    ffff8b55c2693040:    g        16KiB 40 40 [ 0 0 0 0 ] 0  LLC dirty (pinned x 1) (ggtt offset: 02b9f000, size: 00004000, type: 0) (stolen: 00005000)
> >    ffff8b55bf9a7300:    g        16KiB 40 40 [ 0 0 0 0 ] 0  LLC dirty (pinned x 0) (ggtt offset: 0f6b4000, size: 00004000, type: 0) (stolen: 00009000)
> >    ffff8b55a6161040:    g        16KiB 40 40 [ 0 0 0 0 ] 0  LLC dirty (pinned x 0) (ggtt offset: 0937f000, size: 00004000, type: 0) (stolen: 0000d000)
> >    ffff8b5563e0dac0:    g        16KiB 40 40 [ 0 0 0 0 ] 0  LLC dirty (pinned x 0) (ggtt offset: 0f714000, size: 00004000, type: 0) (stolen: 00019000)
> >    ffff8b55bf17e800:    g         4KiB 41 00 [ 0 0 0 0 ] 0  LLC (pinned x 1) (ggtt offset: ffffe000, size: 00001000, type: 0) (stolen: 0012c000)
> >    ffff8b55bf02d540:    g        16KiB 40 40 [ 0 0 0 0 ] 0  LLC dirty (pinned x 1) (ggtt offset: 00141000, size: 00004000, type: 0) (stolen: 0012d000)
> >    ffff8b55c2989340:    g        16KiB 40 40 [ 0 0 0 0 ] 0  LLC dirty (pinned x 1) (ggtt offset: 00148000, size: 00004000, type: 0) (stolen: 00131000)
> >    ffff8b55c29890c0:    g        16KiB 40 40 [ 0 0 0 0 ] 0  LLC dirty (pinned x 1) (ggtt offset: 0014f000, size: 00004000, type: 0) (stolen: 00135000)
> >    ffff8b55c2989840:    g        16KiB 40 40 [ 0 0 0 0 ] 0  LLC dirty (pinned x 1) (ggtt offset: 00156000, size: 00004000, type: 0) (stolen: 00139000)
> >    ffff8b55bf02da40:  p g     14400KiB 77 00 [ 0 0 0 0 ] 0  uncached dirty (name: 1) (pinned x 1) (display) (ggtt offset: 0015a000, size: 00e10000, type: 0) (stolen: 0013d000) (p mappable)
> >    ffff8b556dfba780:    g        16KiB 40 40 [ 0 0 0 0 ] 0  LLC dirty (pinned x 0) (ggtt offset: 0ad2a000, size: 00004000, type: 0) (stolen: 01655000)
> > 
> > > likely you'll have the fbdev framebuffer taking up a sizeable chunk.
> > 
> > Seems 14MB.
> > 
> > > You could get some back by reducing fbdev depth to 16bpp, or even 8bpp,
> > > but I'm not convinced the fbdev gamma LUT stuff really works currently
> > > so you might end up with bogus colors in your vts with that.
> > 
> > Ok, I could try it. Via fbset tool?
> 
> Kernel command line. We don't allow resizing the fbdev fb once it's
> created.

Ok, will try.

> > 
> > > > 
> > > > [    0.000000] Memory: 7972840K/8282704K available (6196K kernel code, 1159K rwdata, 2848K rodata, 1408K init, 688K bss, 309864K reserved, 0K cma-reserved)
> > > > 
> > > > > The BIOS may or may not provide a knob to change the size
> > > > > of the stolen memory.
> > > > 
> > > > In BIOS Setup screen I have option to choose GPU memory and I set it to
> > > > max 512MB. So this is not the right option...
> > > > 
> > > > And why cannot kernel use some continuous check of RAM itself?
> > > 
> > > Because the hardware won't allow it.
> > 
> > So it can be done only once after reboot? Or only prior to booting kernel?
> 
> Never.

Never? Now I'm lost. Why then dmesg message instruct user to try set up
it in BIOS if you say it is never possible?

-- 
Pali Rohár
pali.rohar@...il.com

Download attachment "signature.asc" of type "application/pgp-signature" (196 bytes)