linux-kernel - Re: [PATCH v4] of: fdt: Scan /memreserve/ last

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Date:   Thu, 27 Apr 2023 16:04:17 -0500
From:   Rob Herring <robh@...nel.org>
To:     Lucas Tanure <tanure@...ux.com>
Cc:     linux-arm-kernel@...ts.infradead.org, narmstrong@...libre.com,
        devicetree@...r.kernel.org, Mike Rapoport <rppt@...nel.org>,
        martin.blumenstingl@...glemail.com,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-amlogic@...ts.infradead.org,
        Frank Rowand <frowand.list@...il.com>,
        Rob Herring <robh+dt@...nel.org>, jbrunet@...libre.com,
        stefan@...er.ch, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] of: fdt: Scan /memreserve/ last


On Mon, 24 Apr 2023 12:38:46 +0100, Lucas Tanure wrote:
> Change the scanning /memreserve/ and /reserved-memory node order to fix
> Kernel panic on Khadas Vim3 Board.
> 
> If /memreserve/ goes first, the memory is reserved, but nomap can't be
> applied to the region. So the memory won't be used by Linux, but it is
> still present in the linear map as normal memory, which allows
> speculation. Legitimate access to adjacent pages will cause the CPU
> to end up prefetching into them leading to Kernel panic.
> 
> So /reserved-memory node should go first, as it has a more updated
> description of the memory regions and can apply flags, like nomap.
> 
> Signed-off-by: Lucas Tanure <tanure@...ux.com>i
> ---
> Previous Threads:
> #regzbot link: https://lore.kernel.org/linux-arm-kernel/40ca11f84b7cdbfb9ad2ddd480cb204a@agner.ch/#regzbot
> #regzbot link: https://lore.kernel.org/all/CAJX_Q+1Tjc+-TjZ6JW9X0NxEdFe=82a9626yL63j7uVD4LpxEA@mail.gmail.com/

Note that this should have been a 'Link:' entry in the commit message 
for regzbot. I added it.

> 
> V1: https://lore.kernel.org/all/20230406151429.524591-1-tanure@linux.com/
> v2: https://lore.kernel.org/all/20230410120017.41664-1-tanure@linux.com/
> v3: https://lore.kernel.org/linux-mm/20230412224620.8909-1-tanure@linux.com/T/
> 
> Change from V3:
>  - Drop cover letter
>  - Add more information into the patch
> 
> Change from V2:
>  - Remove region overlap and reserved checks
> 
> Change from V1:
>  - Instead of allowing to mark nomap a region already reserved, give
> precedence to /reserved-memory node scan.
> ---
>  drivers/of/fdt.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 

Applied, thanks!

Going to let this sit in linux-next for a bit. I also didn't tag for 
stable kernels. I want it to get some exposure in mainline at least for 
a few -rc releases rather than getting backported right away. Please 
help ensure that happens if you see stable review emails. I'm going to 
be offline most of the next month.

Rob