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Subject: Re: [PATCH 1/2] m68k: nommu: register start of the memory with
 memblock
From:   Greg Ungerer <gerg@linux-m68k.org>
To:     Mike Rapoport <rppt@kernel.org>
Cc:     Geert Uytterhoeven <geert@linux-m68k.org>,
        linux-m68k@lists.linux-m68k.org, linux-kernel@vger.kernel.org,
        Mike Rapoport <rppt@linux.ibm.com>
References: <20200617065341.32160-1-rppt@kernel.org>
 <20200617065341.32160-2-rppt@kernel.org>
 <45cb9ecf-44c2-d307-4342-e66851ef67a7@linux-m68k.org>
Message-ID: <4a988de6-b194-5831-9eec-3dd7417bc3c7@linux-m68k.org>
Date:   Mon, 29 Jun 2020 11:10:16 +1000
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Hi Mike,

On 17/6/20 10:33 pm, Greg Ungerer wrote:
> Hi Mike,
> 
> On 17/6/20 4:53 pm, Mike Rapoport wrote:
>> From: Mike Rapoport <rppt@linux.ibm.com>
>>
>> The m68k nommu setup code didn't register the beginning of the physical
>> memory with memblock because it was anyway occupied by the kernel. However,
>> commit fa3354e4ea39 ("mm: free_area_init: use maximal zone PFNs rather than
>> zone sizes") changed zones initialization to use memblock.memory to detect
>> the zone extents and this caused inconsistency between zone PFNs and the
>> actual PFNs:
>>
>> BUG: Bad page state in process swapper  pfn:20165
>> page:41fe0ca0 refcount:0 mapcount:1 mapping:00000000 index:0x0 flags: 0x0()
>> raw: 00000000 00000100 00000122 00000000 00000000 00000000 00000000 00000000
>> page dumped because: nonzero mapcount
>> CPU: 0 PID: 1 Comm: swapper Not tainted 5.8.0-rc1-00001-g3a38f8a60c65-dirty #1
>> Stack from 404c9ebc:
>>          404c9ebc 4029ab28 4029ab28 40088470 41fe0ca0 40299e21 40299df1 404ba2a4
>>          00020165 00000000 41fd2c10 402c7ba0 41fd2c04 40088504 41fe0ca0 40299e21
>>          00000000 40088a12 41fe0ca0 41fe0ca4 0000020a 00000000 00000001 402ca000
>>          00000000 41fe0ca0 41fd2c10 41fd2c10 00000000 00000000 402b2388 00000001
>>          400a0934 40091056 404c9f44 404c9f44 40088db4 402c7ba0 00000001 41fd2c04
>>          41fe0ca0 41fd2000 41fe0ca0 40089e02 4026ecf4 40089e4e 41fe0ca0 ffffffff
>> Call Trace:
>>          [<40088470>] 0x40088470
>>   [<40088504>] 0x40088504
>>   [<40088a12>] 0x40088a12
>>   [<402ca000>] 0x402ca000
>>   [<400a0934>] 0x400a0934
>>
>> Adjust the memory registration with memblock to include the beginning of
>> the physical memory and make sure that the area occupied by the kernel is
>> marked as reserved.
>>
>> Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
> 
> Acked-by: Greg Ungerer <gerg@linux-m68k.org>

What path do you anticipate this taking into mainline?
I see it is still broken in 5.8-rc3.

Regards
Greg


>> ---
>>   arch/m68k/kernel/setup_no.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/m68k/kernel/setup_no.c b/arch/m68k/kernel/setup_no.c
>> index e779b19e0193..f66f4b1d062e 100644
>> --- a/arch/m68k/kernel/setup_no.c
>> +++ b/arch/m68k/kernel/setup_no.c
>> @@ -138,7 +138,8 @@ void __init setup_arch(char **cmdline_p)
>>       pr_debug("MEMORY -> ROMFS=0x%p-0x%06lx MEM=0x%06lx-0x%06lx\n ",
>>            __bss_stop, memory_start, memory_start, memory_end);
>> -    memblock_add(memory_start, memory_end - memory_start);
>> +    memblock_add(_rambase, memory_end - _rambase);
>> +    memblock_reserve(_rambase, memory_start - _rambase);
>>       /* Keep a copy of command line */
>>       *cmdline_p = &command_line[0];
>>