linux-kernel - Re: [PATCH v4 1/5] arm64: export memblock

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Message-ID: <dc5a9115-7536-6d72-18fd-60b5322c870c@arm.com>
Date:   Thu, 23 Aug 2018 13:35:08 +0100
From:   James Morse <james.morse@....com>
To:     John Stultz <john.stultz@...aro.org>
Cc:     AKASHI Takahiro <takahiro.akashi@...aro.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        G Gregory <graeme.gregory@...aro.org>, al.stone@...aro.org,
        bhsharma@...hat.com, tbaicar@...eaurora.org,
        kexec@...ts.infradead.org, lkml <linux-kernel@...r.kernel.org>,
        hanjun.guo@...aro.org, Sudeep Holla <sudeep.holla@....com>,
        dyoung@...hat.com,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v4 1/5] arm64: export memblock_reserve()d regions via
 /proc/iomem

Hi John,

On 21/08/18 20:38, John Stultz wrote:
> On Tue, Aug 21, 2018 at 3:22 AM, James Morse <james.morse@....com> wrote:
>> On 08/21/2018 05:39 AM, John Stultz wrote:
>>>
>>> Since this patch landed, on the HiKey board at bootup I'm seeing:
>>>
>>> [    0.451884] WARNING: CPU: 1 PID: 1 at arch/arm64/kernel/setup.c:271
>>> reserve_memblock_reserved_regions+0xd4/0x13c
> ...
>>>  From skimming the patch, it seems this is maybe expected? Or should
>>> this warning raise eyebrows? I can't quite figure it out.
>>

>>> /proc/iomem now has:
>>> ...
>>> 07410000-21efffff : System RAM
>>>    11000000-1113cfff : reserved
>>
>>
>>> 21f00000-21ffffff : reserved
>>
>>
>> ^ This entry is what triggered the warning.
>>
>> It expects that meblock_reserved() memory is also described as memory.
>> (memblock keeps them as separate lists, so its possible to reserve
>> memory that doesn't exist... which it looks like your system is doing)
> 
> So yea, I suspect the hikey dts isn't quite right here then.

The DT mem-reserve code goes and memblock_removes() some regions, instead of
marking them nomap.

Given memblock has a for_each_resv_unavail_range() that explicitly walks
reserved && !memory, it looks like this is expected, and its just me thinking
this is strange.

I will come up with a version of this patch that walks the 'System RAM'
resources that were created during boot, and adds the memblock_reserved()
regions to them, which should stop this happening.


Thanks,

James