Re: Debian SID kernel doesn't boot on PowerBook 3400c

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 31/07/2021 à 20:24, Stan Johnson a écrit :
> Hi Christophe,
> 
> On 7/31/21 9:58 AM, Christophe Leroy wrote:
>> Stan Johnson <userm57@yahoo.com> a écrit :
>>
>>> Hello,
>>>
>>> The current Debian SID kernel will not boot on a PowerBook 3400c running
>>> the latest version of Debian SID. If booted using the BootX extension,
>>> the kernel hangs immediately:
>>>
>>> "Welcome to Linux, kernel 5.10.0-8-powerpc"
>>>
>>> If booted from Mac OS, the Mac OS screen hangs.
>>>
>>> Booting also hangs if the "No video driver" option is selected in BootX,
>>> "No video driver" causes "video=ofonly" to be passed to the kernel.
>>>
>>> This is the current command line that I'm using in BootX:
>>> root=/dev/sda13 video=chips65550:vmode:14,cmode:16
>>>
>>> Kernel v5.9 works as expected.
>>>
>>> The config file I'm using is attached.
>>>
>>> Here are the results of a git bisect, marking v5.9 as "good" and the
>>> most current kernel as "bad":
>>>
>>> $ cd linux
>>> $ git remote update
>>> $ git bisect reset
>>> $ git bisect start
>>> $ git bisect bad
>>> $ git bisect good v5.9
>>>
>>> Note: "bad" -> hangs at boot; "good" -> boots to login prompt
>>>
>>>   1) 5.11.0-rc5-pmac-00034-g684da7628d9 (bad)
>>>   2) 5.10.0-rc3-pmac-00383-gbb9dd3ce617 (good)
>>>   3) 5.10.0-pmac-06637-g2911ed9f47b (good)
>>>      Note: I had to disable SMP to build this kernel.
>>>   4) 5.10.0-pmac-10584-g9805529ec54 (good)
>>>      Note: I had to disable SMP to build this kernel.
>>>   5) 5.10.0-pmac-12577-g8552d28e140 (bad)
>>>   6) 5.10.0-pmac-11576-g8a5be36b930 (bad)
>>>   7) 5.10.0-pmac-11044-gbe695ee29e8 (good)
>>>      Note: I had to disable SMP to build this kernel.
>>>   8) 5.10.0-rc2-pmac-00288-g59d512e4374 (bad)
>>>   9) 5.10.0-rc2-pmac-00155-gc3d35ddd1ec (good)
>>> 10) 5.10.0-rc2-pmac-00221-g7049b288ea8 (good)
>>> 11) 5.10.0-rc2-pmac-00254-g4b74a35fc7e (bad)
>>> 12) 5.10.0-rc2-pmac-00237-ged22bb8d39f (good)
>>> 13) 5.10.0-rc2-pmac-00245-g87b57ea7e10 (good)
>>> 14) 5.10.0-rc2-pmac-00249-gf10881a46f8 (bad)
>>> 15) 5.10.0-rc2-pmac-00247-gf8a4b277c3c (good)
>>> 16) 5.10.0-rc2-pmac-00248-gdb972a3787d (bad)
>>>
>>> db972a3787d12b1ce9ba7a31ec376d8a79e04c47 is the first bad commit
>>
>> Not sure this is really the root of the problem.
>>
>> Can you try again without CONFIG_VMAP_STACK ?
>>
>> Thanks
>> Christophe
>> ...
> 
> 
> With CONFIG_VMAP_STACK=y, 5.11.0-rc5-pmac-00034-g684da7628d9 hangs at
> boot on the PB 3400c.
> 
> Without CONFIG_VMAP_STACK, 5.11.0-rc5-pmac-00034-g684da7628d9 boots as
> expected.
> 
> I didn't re-build the Debian SID kernel, though I confirmed that the
> Debian config file for 5.10.0-8-powerpc includes CONFIG_VMAP_STACK=y.
> It's not clear whether removing CONFIG_VMAP_STACK would be appropriate
> for other powerpc systems.
> 
> Please let me know why removing CONFIG_VMAP_STACK fixed the problem on
> the PB 3400c. Should CONFIG_HAVE_ARCH_VMAP_STACK also be removed?
> 

When CONFIG_HAVE_ARCH_VMAP_STACK is selected by the architecture, CONFIG_VMAP_STACK  is selected by 
default.

The point is that your config has CONFIG_ADB_PMU.

A bug with VMAP stack was detected during 5.9 release cycle for platforms selecting CONFIG_ADB_PMU. 
Because fixing the bug was an heavy change, we prefered at that time to disable VMAP stack, so VMAP 
stack was deselected for CONFIG_ADB_PMU by commit 4a133eb351ccc275683ad49305d0b04dde903733.

Then as a second step, the proper fix was implemented and then VMAP stack was enabled again by the 
commit you bisected.

Taking into account that the problem disappears for you when you manually deselect VMAP stacks, it 
means the problem is not the fix itself, but the fact that VMAP stacks are now enable by default.

We need to understand why VMAP stack doesn't work on your platform, more than that why it doesn't 
boot at all with VMAP stack.

Could you send me the dmesg output of your system when it properly boots ?

Did you check with kernel 5.13 ?

Thanks
Christophe