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

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Message-ID: <YJkGSb72aKg6ScGo@google.com>
Date:   Mon, 10 May 2021 10:09:13 +0000
From:   Quentin Perret <qperret@...gle.com>
To:     Alexandre TORGUE <alexandre.torgue@...s.st.com>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Sasha Levin <sashal@...nel.org>,
        stable <stable@...r.kernel.org>, Arnd Bergmann <arnd@...db.de>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Nicolas Boichat <drinkcat@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        KarimAllah Ahmed <karahmed@...zon.de>,
        Android Kernel Team <kernel-team@...roid.com>,
        Architecture Mailman List <boot-architecture@...ts.linaro.org>,
        Frank Rowand <frowand.list@...il.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [v5.4 stable] arm: stm32: Regression observed on "no-map"
 reserved memory region

Hi Alexandre,

On Friday 07 May 2021 at 17:15:20 (+0200), Alexandre TORGUE wrote:
> Did you get time to continue some tests on this issue ?

I did try a few things, but still fail to reproduced :/

> On my side this DT is not working:
> 
> memory@...00000 {
>         reg = <0xc0000000 0x20000000>;
> };
> 
> reserved-memory {
>         #address-cells = <1>;
>         #size-cells = <1>;
>         ranges;
> 
>         gpu_reserved: gpu@...00000 {
>                 reg = <0xd4000000 0x4000000>;
>                 no-map;
>         };
> };

So this does change how memory appears in /proc/iomem for me switching
from 5.4.101 to v5.4.102 -- for the former d4000000-d7ffffff doesn't
appear at all, and for the latter it appears as 'reserved'.

But still, it never gets accounted as System RAM for me ...

> Let me know if I can help.

Could you please confirm you get a correct behaviour with 5.10.31 like
Florian? If so, then bisecting to figure out what we're missing in older
LTSes would help, but again it feels like we should just revert -- this
wasn't really a fix in the first place.

Thanks,
Quentin