[Bug 84431] New: Kernel crash when unloading radeon module for switcheroo card

[Bug 84431] New: Kernel crash when unloading radeon module for switcheroo card

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=84431

            Bug ID: 84431
           Summary: Kernel crash when unloading radeon module for
                    switcheroo card
           Product: Drivers
           Version: 2.5
    Kernel Version: all
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: high
          Priority: P1
         Component: Video(DRI - non Intel)
          Assignee: drivers_video-dri@kernel-bugs.osdl.org
          Reporter: pali.rohar@gmail.com
        Regression: No

Created attachment 149991
  --> https://bugzilla.kernel.org/attachment.cgi?id=149991&action=edit
Fix crash after rmmod radeon on PX systems.

Calling rmmod radeon on PX system cause kernel crash. Reason is function
vga_switcheroo_init_domain_pm_ops() which setting dev->pm_domain function of
PCI device. When radeon module is unloaded pointer dev->pm_domain is set to
vga_switcheroo function which try to call radeon function (which does not
exists in memory after rmmod radeon). I bet that nouveau has same problem.

I'm attaching simple patch which set dev->pm_domain of PCI device back to NULL
when removing radeon device so vga_switcheroo will not be called.

But I think that proper way for fixing this bug - which is in vga_switcheroo -
should be to add function like "vga_switcheroo_exit_domain_pm_ops()" which will
set pm_domain back to origin value (which is in my case NULL).

With my patch on PX system I can call rmmod radeon, modprobe radeon, rmmod
radeon, ... many times without no crash.

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[Bug 84431] Kernel crash when unloading radeon module for switcheroo card

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https://bugzilla.kernel.org/show_bug.cgi?id=84431

Pali Rohár <pali.rohar@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
 Attachment #149991|0                           |1
           is patch|                            |
 Attachment #149991|application/octet-stream    |text/plain
          mime type|                            |

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[Bug 84431] Kernel crash when unloading radeon module for switcheroo card

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=84431

Alex Deucher <alexdeucher@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |alexdeucher@gmail.com

--- Comment #1 from Alex Deucher <alexdeucher@gmail.com> ---
Care to generate a git patch and sign-off on it?

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[Bug 84431] Kernel crash when unloading radeon module for switcheroo card

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https://bugzilla.kernel.org/show_bug.cgi?id=84431

--- Comment #2 from Pali Rohár <pali.rohar@gmail.com> ---
I can, but I do not know if this is proper way how to fix it. I still think
that root of bug is in function vga_switcheroo_init_domain_pm_ops() which
overwrite dev->pm_domain, but does not restore it when driver/device
unregister.

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[Bug 84431] Kernel crash when unloading radeon module for switcheroo card

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=84431

--- Comment #3 from Alex Deucher <alexdeucher@gmail.com> ---
Created attachment 150001
  --> https://bugzilla.kernel.org/attachment.cgi?id=150001&action=edit
patch 1/3

How about this patch set?

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[Bug 84431] Kernel crash when unloading radeon module for switcheroo card

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https://bugzilla.kernel.org/show_bug.cgi?id=84431

--- Comment #4 from Alex Deucher <alexdeucher@gmail.com> ---
Created attachment 150011
  --> https://bugzilla.kernel.org/attachment.cgi?id=150011&action=edit
patch 2/3

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[Bug 84431] Kernel crash when unloading radeon module for switcheroo card

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https://bugzilla.kernel.org/show_bug.cgi?id=84431

--- Comment #5 from Alex Deucher <alexdeucher@gmail.com> ---
Created attachment 150021
  --> https://bugzilla.kernel.org/attachment.cgi?id=150021&action=edit
patch 3/3

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[Bug 84431] Kernel crash when unloading radeon module for switcheroo card

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https://bugzilla.kernel.org/show_bug.cgi?id=84431

--- Comment #6 from Pali Rohár <pali.rohar@gmail.com> ---
I tested 1/3 and 2/3 on 3.13 kernel. And as expected (because patches doing
same thing) same result as with my patch - no kernel crash anymore. You can add
my Signed-off.

I do not have nvidia optimus card, so I cannot test last patch.

Anyway in vga_switcheroo.c is exported function
vga_switcheroo_init_domain_pm_optimus_hdmi_audio() which changing
dev->pm_domain too. But I do not see any driver which using it.

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[Bug 84431] Kernel crash when unloading radeon module for switcheroo card

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=84431

--- Comment #7 from Pali Rohár <pali.rohar@gmail.com> ---
Function vga_switcheroo_init_domain_pm_optimus_hdmi_audio() is used in
sound/pci/hda/hda_intel.c. So that driver has same problem and cause kernel
panic on driver unload.

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[Bug 84431] Kernel crash when unloading radeon module for switcheroo card

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=84431

Joaquín Aramendía <samsagax@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |samsagax@gmail.com

--- Comment #8 from Joaquín Aramendía <samsagax@gmail.com> ---
Alex, That patchset indeed got rid of that bug, but for some reason it
introduced another one:
https://bugzilla.kernel.org/show_bug.cgi?id=86011

97d30fa3524ff60b43d450012abe8f961d280478 from stable kernel tree breaks nouveau
power management through vga-switcheroo.

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[Bug 84431] Kernel crash when unloading radeon module for switcheroo card

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=84431

Peter Wu <peter@lekensteyn.nl> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |peter@lekensteyn.nl

--- Comment #9 from Peter Wu <peter@lekensteyn.nl> ---
(In reply to Pali Rohár from comment #7)
> Function vga_switcheroo_init_domain_pm_optimus_hdmi_audio() is used in
> sound/pci/hda/hda_intel.c. So that driver has same problem and cause kernel
> panic on driver unload.

A patch for this issue is queued at
http://mailman.alsa-project.org/pipermail/alsa-devel/2016-July/110125.html

Joaquín, how does 97d30fa35 break nouveau vga-switcheroo? If you load nouveau
with runpm=0, then you can write OFF to debugfs' vga_switcheroo. However
runpm=1 (or -1 for Optimus systems) is recommended.

I think that the original bug is fixed, so this can be marked as resolved?

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[Bug 84431] Kernel crash when unloading radeon module for switcheroo card

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=84431

--- Comment #10 from Joaquín Aramendía <samsagax@gmail.com> ---

> Joaquín, how does 97d30fa35 break nouveau vga-switcheroo? If you load
> nouveau with runpm=0, then you can write OFF to debugfs' vga_switcheroo.
> However runpm=1 (or -1 for Optimus systems) is recommended.

Just tested removing nouveau module with Ubuntu 16.04 on mainline kernel v4.6.5
and it worked correctly. Also modprobed it after that and worked correctly.
This bug should be marked as resolved.

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