[Bug 206501] New: Kernel 5.6-rc1 fails to boot on a PowerMac G4 3,6 with CONFIG_VMAP_STACK=y: Oops! Machine check, sig: 7 [#1]

[Bug 206501] New: Kernel 5.6-rc1 fails to boot on a PowerMac G4 3,6 with CONFIG_VMAP_STACK=y: Oops! Machine check, sig: 7 [#1]

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=206501

            Bug ID: 206501
           Summary: Kernel 5.6-rc1 fails to boot on a PowerMac G4 3,6 with
                    CONFIG_VMAP_STACK=y: Oops! Machine check, sig: 7  [#1]
           Product: Platform Specific/Hardware
           Version: 2.5
    Kernel Version: 5.6.0-rc1
          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 287311
  --> https://bugzilla.kernel.org/attachment.cgi?id=287311&action=edit
screenshot

The G4 boots fine with CONFIG_VMAP_STACK=n, but fails to boot with
CONFIG_VMAP_STACK=y.

[...]
NIP [c001c194] create_hpte+0xa8/0x120
LR [c001c0c4] add_hash_page+0x88/0xb0
Call Trace:
[f101dde8] [cO181568] alloc_set_pte+0x184/0x214 (unreliable)
[f101de18] [cO14d168] filemap_map_pages+0x21c/0x250
[f101de68] [c0181cf4] handle_mm_fault+0x66c/0x90c
[f101dee8] [c0019aac] do_page_fault+0x690/0x804
[f101df38] [c0014450] handle_page_fault+0x10/0x3c
--- interrupt: 401 at Oxb77ffd10
    LR = 0x0
Instruction dump:
6c64003f 6884ffx0 3884fff8 7c0903a6 84x40008 7c062800 4002fff8 41a2008c
68a50040 7c0903a6 3883fff8 84c40008 <54c60001> 4002fff8 41a20070 3c80c08e
---[ end trace cd24dd23c7db9d53 ]---

Machine check in kernel mode.
Caused by (from SRR1=141020): Transfer error ack signal
Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000007

(OCRed screenshot + corrections by hand)

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[Bug 206501] Kernel 5.6-rc1 fails to boot on a PowerMac G4 3,6 with CONFIG_VMAP_STACK=y: Oops! Machine check, sig: 7 [#1]

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=206501

--- Comment #1 from Erhard F. (erhard_f@mailbox.org) ---
Created attachment 287313
  --> https://bugzilla.kernel.org/attachment.cgi?id=287313&action=edit
kernel .config (5.6.0-rc1, PowerMac G4 DP)

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[Bug 206501] Kernel 5.6-rc1 fails to boot on a PowerMac G4 3,6 with CONFIG_VMAP_STACK=y: Oops! Machine check, sig: 7 [#1]

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=206501

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) ---
Created attachment 287321
  --> https://bugzilla.kernel.org/attachment.cgi?id=287321&action=edit
powerpc/32s: Fix add_hash_page() for CONFIG_VMAP_STACK

Please test this patch.

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[Bug 206501] Kernel 5.6-rc1 fails to boot on a PowerMac G4 3,6 with CONFIG_VMAP_STACK=y: Oops! Machine check, sig: 7 [#1]

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=206501

--- Comment #3 from Christophe Leroy (christophe.leroy@c-s.fr) ---
Could you also test the patch https://patchwork.ozlabs.org/patch/1236804/
instead of the above patch.

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[Bug 206501] Kernel 5.6-rc1 fails to boot on a PowerMac G4 3,6 with CONFIG_VMAP_STACK=y: Oops! Machine check, sig: 7 [#1]

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=206501

--- Comment #4 from Erhard F. (erhard_f@mailbox.org) ---
Created attachment 287329
  --> https://bugzilla.kernel.org/attachment.cgi?id=287329&action=edit
dmesg (5.6.0-rc1 + Fix DSI and ISI... patch , PowerMac G4 DP)

First patch was not successful, I got no stacktrace but the boot process still
got still stuck.

Second patch was succesful to the point where the G4 was able to boot up to the
point of revealing a dmesg full of other problems, e.g. some 'Unrecoverable
exceptions' ;)

Please find the dmesg attached.

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[Bug 206501] Kernel 5.6-rc1 fails to boot on a PowerMac G4 3,6 with CONFIG_VMAP_STACK=y: Oops! Machine check, sig: 7 [#1]

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=206501

--- Comment #5 from Christophe Leroy (christophe.leroy@c-s.fr) ---
Interesting.

NIP:  00000550
NIP:  0000045c
NIP:  00000c38
NIP:  00000370

The kernel seems to badly fault on the first write to the stack. This suggests
that there is no page allocated for the stack yet. Which is unexpected because
in copy_thread_tls() several writes to the stack are performed so the pages
must exist in page tables.

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[Bug 206501] Kernel 5.6-rc1 fails to boot on a PowerMac G4 3,6 with CONFIG_VMAP_STACK=y: Oops! Machine check, sig: 7 [#1]

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https://bugzilla.kernel.org/show_bug.cgi?id=206501

--- Comment #6 from Christophe Leroy (christophe.leroy@c-s.fr) ---
I found the reason I think. I just realised that the things saved to SPRN_SPRG
and in thread struct get overwriten by the DSI taken at stack write.

I'll prepare something to fix that.

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[Bug 206501] Kernel 5.6-rc1 fails to boot on a PowerMac G4 3,6 with CONFIG_VMAP_STACK=y: Oops! Machine check, sig: 7 [#1]

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=206501

--- Comment #7 from Christophe Leroy (christophe.leroy@c-s.fr) ---
Can you try version v2 of the patch,
https://patchwork.ozlabs.org/patch/1237387/

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[Bug 206501] Kernel 5.6-rc1 fails to boot on a PowerMac G4 3,6 with CONFIG_VMAP_STACK=y: Oops! Machine check, sig: 7 [#1]

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=206501

--- Comment #8 from Erhard F. (erhard_f@mailbox.org) ---
(In reply to Christophe Leroy from comment #7)
> Can you try version v2 of the patch,
> https://patchwork.ozlabs.org/patch/1237387/
I can confirm that v2 works as intended. The G4 completes booting with
VMAP_STACK enabled and without producing further stack traces. Thanks!

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[Bug 206501] Kernel 5.6-rc1 fails to boot on a PowerMac G4 3,6 with CONFIG_VMAP_STACK=y: Oops! Machine check, sig: 7 [#1]

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https://bugzilla.kernel.org/show_bug.cgi?id=206501

--- Comment #9 from Christophe Leroy (christophe.leroy@c-s.fr) ---
Great. Can we add your Tested-by: to the commit ?

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[Bug 206501] Kernel 5.6-rc1 fails to boot on a PowerMac G4 3,6 with CONFIG_VMAP_STACK=y: Oops! Machine check, sig: 7 [#1]

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--- Comment #10 from Erhard F. (erhard_f@mailbox.org) ---
Sure. Thanks!

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[Bug 206501] Kernel 5.6-rc1 fails to boot on a PowerMac G4 3,6 with CONFIG_VMAP_STACK=y: Oops! Machine check, sig: 7 [#1]

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=206501

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

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

--- Comment #11 from Erhard F. (erhard_f@mailbox.org) ---
Fix landed in 5.6-rc3, works now as expected. Thanks!

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