[Bug 203597] New: kernel 4.9.175 fails to boot on a PowerMac G4 3,6 at early stage

[Bug 203597] New: kernel 4.9.175 fails to boot on a PowerMac G4 3,6 at early stage

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203597

            Bug ID: 203597
           Summary: kernel 4.9.175 fails to boot on a PowerMac G4 3,6 at
                    early stage
           Product: Platform Specific/Hardware
           Version: 2.5
    Kernel Version: 4.9.175
          Hardware: PPC-32
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: PPC-32
          Assignee: platform_ppc-32@kernel-bugs.osdl.org
          Reporter: erhard_f@mailbox.org
        Regression: No

Created attachment 282743
  --> https://bugzilla.kernel.org/attachment.cgi?id=282743&action=edit
kernel .config (PowerMac G4 MDD)

Trying out older kernels on the G4 MDD I noticed recent 4.9.x freeze the
machine. Only message displayed in black letters on a white screen:

done
found display   : /pco@f0000000/ATY,AlteracParent@10/ATY,Alterac_B@1,
opening...


It's a hard freeze, RCU_CPU_STALL_TIMEOUT does not kick in.

Tried other stable kernels, which all worked:
4.19.37
4.14.114 
4.4.179

So I suppose it's only a 4.9.x issue. Last working 4.9.x kernel I had in
service was 4.9.161. First one I spotted freezing was 4.9.171. A bisect gave me
the following commit:

1c38a84d45862be06ac418618981631eddbda741 is the first bad commit
commit 1c38a84d45862be06ac418618981631eddbda741
Author: Michael Neuling <mikey@neuling.org>
Date:   Thu Apr 11 21:45:59 2019 +1000

    powerpc: Avoid code patching freed init sections

    commit 51c3c62b58b357e8d35e4cc32f7b4ec907426fe3 upstream.

    This stops us from doing code patching in init sections after they've
    been freed.

    In this chain:
      kvm_guest_init() ->
        kvm_use_magic_page() ->
          fault_in_pages_readable() ->
             __get_user() ->
               __get_user_nocheck() ->
                 barrier_nospec();

    We have a code patching location at barrier_nospec() and
    kvm_guest_init() is an init function. This whole chain gets inlined,
    so when we free the init section (hence kvm_guest_init()), this code
    goes away and hence should no longer be patched.

    We seen this as userspace memory corruption when using a memory
    checker while doing partition migration testing on powervm (this
    starts the code patching post migration via
    /sys/kernel/mobility/migration). In theory, it could also happen when
    using /sys/kernel/debug/powerpc/barrier_nospec.

    Cc: stable@vger.kernel.org # 4.13+
    Signed-off-by: Michael Neuling <mikey@neuling.org>
    Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
    Reviewed-by: Christophe Leroy <christophe.leroy@c-s.fr>
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Signed-off-by: Sasha Levin <sashal@kernel.org>

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[Bug 203597] kernel 4.9.175 fails to boot on a PowerMac G4 3,6 at early stage

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203597

--- Comment #1 from Erhard F. (erhard_f@mailbox.org) ---
Created attachment 282745
  --> https://bugzilla.kernel.org/attachment.cgi?id=282745&action=edit
bisect.log

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[Bug 203597] kernel 4.9.175 fails to boot on a PowerMac G4 3,6 at early stage

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203597

Christophe Leroy (christophe.leroy@c-s.fr) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |christophe.leroy@c-s.fr

--- Comment #2 from Christophe Leroy (christophe.leroy@c-s.fr) ---
You are missing following commit:

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b45ba4a51cd

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Re: [Bug 203597] New: kernel 4.9.175 fails to boot on a PowerMac G4 3,6 at early stage

[Christophe Leroy]

Hi Greg,

Could you please apply b45ba4a51cde29b2939365ef0c07ad34c8321789 to 4.9 
since 51c3c62b58b357e8d35e4cc32f7b4ec907426fe3 was applied allthought 
marked for #4.13+

Thanks
Christophe

Le 13/05/2019 à 22:18, bugzilla-daemon@bugzilla.kernel.org a écrit :
> https://bugzilla.kernel.org/show_bug.cgi?id=203597
> 
>              Bug ID: 203597
>             Summary: kernel 4.9.175 fails to boot on a PowerMac G4 3,6 at
>                      early stage
>             Product: Platform Specific/Hardware
>             Version: 2.5
>      Kernel Version: 4.9.175
>            Hardware: PPC-32
>                  OS: Linux
>                Tree: Mainline
>              Status: NEW
>            Severity: normal
>            Priority: P1
>           Component: PPC-32
>            Assignee: platform_ppc-32@kernel-bugs.osdl.org
>            Reporter: erhard_f@mailbox.org
>          Regression: No
> 
> Created attachment 282743
>    --> https://bugzilla.kernel.org/attachment.cgi?id=282743&action=edit
> kernel .config (PowerMac G4 MDD)
> 
> Trying out older kernels on the G4 MDD I noticed recent 4.9.x freeze the
> machine. Only message displayed in black letters on a white screen:
> 
> done
> found display   : /pco@f0000000/ATY,AlteracParent@10/ATY,Alterac_B@1,
> opening...
> 
> 
> It's a hard freeze, RCU_CPU_STALL_TIMEOUT does not kick in.
> 
> Tried other stable kernels, which all worked:
> 4.19.37
> 4.14.114
> 4.4.179
> 
> So I suppose it's only a 4.9.x issue. Last working 4.9.x kernel I had in
> service was 4.9.161. First one I spotted freezing was 4.9.171. A bisect gave me
> the following commit:
> 
> 1c38a84d45862be06ac418618981631eddbda741 is the first bad commit
> commit 1c38a84d45862be06ac418618981631eddbda741
> Author: Michael Neuling <mikey@neuling.org>
> Date:   Thu Apr 11 21:45:59 2019 +1000
> 
>      powerpc: Avoid code patching freed init sections
> 
>      commit 51c3c62b58b357e8d35e4cc32f7b4ec907426fe3 upstream.
> 
>      This stops us from doing code patching in init sections after they've
>      been freed.
> 
>      In this chain:
>        kvm_guest_init() ->
>          kvm_use_magic_page() ->
>            fault_in_pages_readable() ->
>               __get_user() ->
>                 __get_user_nocheck() ->
>                   barrier_nospec();
> 
>      We have a code patching location at barrier_nospec() and
>      kvm_guest_init() is an init function. This whole chain gets inlined,
>      so when we free the init section (hence kvm_guest_init()), this code
>      goes away and hence should no longer be patched.
> 
>      We seen this as userspace memory corruption when using a memory
>      checker while doing partition migration testing on powervm (this
>      starts the code patching post migration via
>      /sys/kernel/mobility/migration). In theory, it could also happen when
>      using /sys/kernel/debug/powerpc/barrier_nospec.
> 
>      Cc: stable@vger.kernel.org # 4.13+
>      Signed-off-by: Michael Neuling <mikey@neuling.org>
>      Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
>      Reviewed-by: Christophe Leroy <christophe.leroy@c-s.fr>
>      Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
>      Signed-off-by: Sasha Levin <sashal@kernel.org>
> 

Re: [Bug 203597] New: kernel 4.9.175 fails to boot on a PowerMac G4 3,6 at early stage

[Greg KH]

On Tue, May 14, 2019 at 06:56:03AM +0200, Christophe Leroy wrote:
> Hi Greg,
> 
> Could you please apply b45ba4a51cde29b2939365ef0c07ad34c8321789 to 4.9 since
> 51c3c62b58b357e8d35e4cc32f7b4ec907426fe3 was applied allthought marked for
> #4.13+

It does not apply there (nor to the 4.4.y queue, which will need it as
well), so can you provide a working backport so that I can queue it up?

thanks,

greg k-h

[Bug 203597] kernel 4.9.175 fails to boot on a PowerMac G4 3,6 at early stage

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203597

Erhard F. (erhard_f@mailbox.org) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |CODE_FIX

--- Comment #3 from Erhard F. (erhard_f@mailbox.org) ---
(In reply to Christophe Leroy from comment #2)
> You are missing following commit:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/
> ?id=b45ba4a51cd
Your fix landed in 4.9.177 and I can confirm my G4 boots fine now. Thanks!

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[Bug 203597] kernel 4.9.175 fails to boot on a PowerMac G4 3,6 at early stage

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203597

Michael Ellerman (michael@ellerman.id.au) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |CLOSED
                 CC|                            |michael@ellerman.id.au

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