Re: [v5.4 stable] arm: stm32: Regression observed on "no-map" reserved memory region

[Florian Fainelli]

On 4/21/2021 1:31 AM, Quentin Perret wrote:
> On Tuesday 20 Apr 2021 at 09:33:56 (-0700), Florian Fainelli wrote:
>> I do wonder as well, we have a 32MB "no-map" reserved memory region on
>> our platforms located at 0xfe000000. Without the offending commit,
>> /proc/iomem looks like this:
>>
>> 40000000-fdffefff : System RAM
>>   40008000-40ffffff : Kernel code
>>   41e00000-41ef1d77 : Kernel data
>> 100000000-13fffffff : System RAM
>>
>> and with the patch applied, we have this:
>>
>> 40000000-fdffefff : System RAM
>>   40008000-40ffffff : Kernel code
>>   41e00000-41ef3db7 : Kernel data
>> fdfff000-ffffffff : System RAM
>> 100000000-13fffffff : System RAM
>>
>> so we can now see that the region 0xfe000000 - 0xfffffff is also cobbled
>> up with the preceding region which is a mailbox between Linux and the
>> secure monitor at 0xfdfff000 and of size 4KB. It seems like there is
>>
>> The memblock=debug outputs is also different:
>>
>> [    0.000000] MEMBLOCK configuration:
>> [    0.000000]  memory size = 0xfdfff000 reserved size = 0x7ce4d20d
>> [    0.000000]  memory.cnt  = 0x2
>> [    0.000000]  memory[0x0]     [0x00000040000000-0x000000fdffefff],
>> 0xbdfff000 bytes flags: 0x0
>> [    0.000000]  memory[0x1]     [0x00000100000000-0x0000013fffffff],
>> 0x40000000 bytes flags: 0x0
>> [    0.000000]  reserved.cnt  = 0x6
>> [    0.000000]  reserved[0x0]   [0x00000040003000-0x0000004000e494],
>> 0xb495 bytes flags: 0x0
>> [    0.000000]  reserved[0x1]   [0x00000040200000-0x00000041ef1d77],
>> 0x1cf1d78 bytes flags: 0x0
>> [    0.000000]  reserved[0x2]   [0x00000045000000-0x000000450fffff],
>> 0x100000 bytes flags: 0x0
>> [    0.000000]  reserved[0x3]   [0x00000047000000-0x0000004704ffff],
>> 0x50000 bytes flags: 0x0
>> [    0.000000]  reserved[0x4]   [0x000000c2c00000-0x000000fdbfffff],
>> 0x3b000000 bytes flags: 0x0
>> [    0.000000]  reserved[0x5]   [0x00000100000000-0x0000013fffffff],
>> 0x40000000 bytes flags: 0x0
>>
>> [    0.000000] MEMBLOCK configuration:
>> [    0.000000]  memory size = 0x100000000 reserved size = 0x7ca4f24d
>> [    0.000000]  memory.cnt  = 0x3
>> [    0.000000]  memory[0x0]     [0x00000040000000-0x000000fdffefff],
>> 0xbdfff000 bytes flags: 0x0
>> [    0.000000]  memory[0x1]     [0x000000fdfff000-0x000000ffffffff],
>> 0x2001000 bytes flags: 0x4
>> [    0.000000]  memory[0x2]     [0x00000100000000-0x0000013fffffff],
>> 0x40000000 bytes flags: 0x0
>> [    0.000000]  reserved.cnt  = 0x6
>> [    0.000000]  reserved[0x0]   [0x00000040003000-0x0000004000e494],
>> 0xb495 bytes flags: 0x0
>> [    0.000000]  reserved[0x1]   [0x00000040200000-0x00000041ef3db7],
>> 0x1cf3db8 bytes flags: 0x0
>> [    0.000000]  reserved[0x2]   [0x00000045000000-0x000000450fffff],
>> 0x100000 bytes flags: 0x0
>> [    0.000000]  reserved[0x3]   [0x00000047000000-0x0000004704ffff],
>> 0x50000 bytes flags: 0x0
>> [    0.000000]  reserved[0x4]   [0x000000c3000000-0x000000fdbfffff],
>> 0x3ac00000 bytes flags: 0x0
>> [    0.000000]  reserved[0x5]   [0x00000100000000-0x0000013fffffff],
>> 0x40000000 bytes flags: 0x0
>>
>> in the second case we can clearly see that the 32MB no-map region is now
>> considered as usable RAM.
>>
>> Hope this helps.
>>
>>>
>>> In any case, the mere fact that this causes a regression should be
>>> sufficient justification to revert/withdraw it from v5.4, as I don't
>>> see a reason why it was merged there in the first place. (It has no
>>> fixes tag or cc:stable)
>>
>> Agreed, however that means we still need to find out whether a more
>> recent kernel is also broken, I should be able to tell you that a little
>> later.
> 
> FWIW I did test this on Qemu before posting. With 5.12-rc8 and a 1MiB
> no-map region at 0x80000000, I have the following:
> 
> 40000000-7fffffff : System RAM
>   40210000-417fffff : Kernel code
>   41800000-41daffff : reserved
>   41db0000-4210ffff : Kernel data
>   48000000-48008fff : reserved
> 80000000-800fffff : reserved
> 80100000-13fffffff : System RAM
>   fa000000-ffffffff : reserved
>   13b000000-13f5fffff : reserved
>   13f6de000-13f77dfff : reserved
>   13f77e000-13f77efff : reserved
>   13f77f000-13f7dafff : reserved
>   13f7dd000-13f7defff : reserved
>   13f7df000-13f7dffff : reserved
>   13f7e0000-13f7f3fff : reserved
>   13f7f4000-13f7fdfff : reserved
>   13f7fe000-13fffffff : reserved
> 
> If I remove the 'no-map' qualifier from DT, I get this:
> 
> 40000000-13fffffff : System RAM
>   40210000-417fffff : Kernel code
>   41800000-41daffff : reserved
>   41db0000-4210ffff : Kernel data
>   48000000-48008fff : reserved
>   80000000-800fffff : reserved
>   fa000000-ffffffff : reserved
>   13b000000-13f5fffff : reserved
>   13f6de000-13f77dfff : reserved
>   13f77e000-13f77efff : reserved
>   13f77f000-13f7dafff : reserved
>   13f7dd000-13f7defff : reserved
>   13f7df000-13f7dffff : reserved
>   13f7e0000-13f7f3fff : reserved
>   13f7f4000-13f7fdfff : reserved
>   13f7fe000-13fffffff : reserved
> 
> So this does seem to be working fine on my setup. I'll try again with
> 5.4 to see if I can repro.
> 
> Also, 8a5a75e5e9e5 ("of/fdt: Make sure no-map does not remove already
> reserved regions") looks more likely to cause the issue observed here,
> but that shouldn't be silent. I get the following error message in dmesg
> if I if place the no-map region on top of the kernel image:
> 
> OF: fdt: Reserved memory: failed to reserve memory for node 'foobar@40210000': base 0x0000000040210000, size 1 MiB
> 
> Is that triggering on your end?

It is not, otherwise I would have noticed earlier, can you try the same
thing that happens on my platform with a reserved region (without
no-map) adjacent to a reserved region with 'no-map'? I will test
different and newer kernels than 5.4 today to find out if this is still
a problem with upstream. I could confirm that v4.9.259 also have this
problem now.
-- 
Florian