KASAN debug kernel fails to boot at early stage when CONFIG_SMP=y is set (kernel 6.5-rc5, PowerMac G4 3,6)

[Christophe Leroy]

Le 18/08/2023 à 18:23, Erhard Furtner a écrit :
> On Fri, 18 Aug 2023 15:47:38 +0000
> Christophe Leroy <christophe.leroy at csgroup.eu> wrote:
> 
>> I'm wondering if the problem is just linked to the kernel being built
>> with CONFIG_SMP or if it is the actual startup of a secondary CPU that
>> cause the freeze.
>>
>> Please leave the btext_unmap() in place because I think it is important
>> to keep it, and start the kernel with the following parameter:
>>
>> nr_cpus=1
> 
> With btext_unmap() back and place and nr_cpus=1 set the freeze still happens after the 1st btext_unmap:129 on cold boots:
> 
> [    0.000000] printk: bootconsole [udbg0] enabled
> [    0.000000] Total memory = 2048MB; using 4096kB for hash table
> [    0.000000] mapin_ram:125
> [    0.000000] mmu_mapin_ram:169 0 30000000 1400000 2000000
> [    0.000000] __mmu_mapin_ram:146 0 1400000
> [    0.000000] __mmu_mapin_ram:155 1400000
> [    0.000000] __mmu_mapin_ram:146 1400000 30000000
> [    0.000000] __mmu_mapin_ram:155 20000000
> [    0.000000] __mapin_ram_chunk:107 20000000 30000000
> [    0.000000] __mapin_ram_chunk:117
> [    0.000000] mapin_ram:134
> [    0.000000] kasan_mmu_init:129
> [    0.000000] kasan_mmu_init:132 0
> [    0.000000] kasan_mmu_init:137
> [    0.000000] btext_unmap:129
> 


Thanks,

Can you replace the call to btext_unmap() by a call to btext_map() at 
the end of MMU_init() ?

If that gives no interesting result, can you leave the call to 
btext_unmap() and add a call to btext_map() at the very begining of 
function start_kernel() in init/main.c (You may have to add a include of 
asm/btext.h)

With that I hope we can see more stuff.

Christophe