From: Rob Herring <robh@kernel.org>
To: Quentin Perret <qperret@google.com>
Cc: robh+dt@kernel.org, drinkcat@chromium.org,
devicetree@vger.kernel.org, f.fainelli@gmail.com,
swboyd@chromium.org, karahmed@amazon.de, kernel-team@android.com,
frowand.list@gmail.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] of/fdt: Make sure no-map does not remove already reserved regions
Date: Fri, 15 Jan 2021 11:30:15 -0600 [thread overview]
Message-ID: <20210115173015.GA1496104@robh.at.kernel.org> (raw)
In-Reply-To: <20210115114544.1830068-3-qperret@google.com>
On Fri, 15 Jan 2021 11:45:44 +0000, Quentin Perret wrote:
> From: Nicolas Boichat <drinkcat@chromium.org>
>
> If the device tree is incorrectly configured, and attempts to
> define a "no-map" reserved memory that overlaps with the kernel
> data/code, the kernel would crash quickly after boot, with no
> obvious clue about the nature of the issue.
>
> For example, this would happen if we have the kernel mapped at
> these addresses (from /proc/iomem):
> 40000000-41ffffff : System RAM
> 40080000-40dfffff : Kernel code
> 40e00000-411fffff : reserved
> 41200000-413e0fff : Kernel data
>
> And we declare a no-map shared-dma-pool region at a fixed address
> within that range:
> mem_reserved: mem_region {
> compatible = "shared-dma-pool";
> reg = <0 0x40000000 0 0x01A00000>;
> no-map;
> };
>
> To fix this, when removing memory regions at early boot (which is
> what "no-map" regions do), we need to make sure that the memory
> is not already reserved. If we do, __reserved_mem_reserve_reg
> will throw an error:
> [ 0.000000] OF: fdt: Reserved memory: failed to reserve memory
> for node 'mem_region': base 0x0000000040000000, size 26 MiB
> and the code that will try to use the region should also fail,
> later on.
>
> We do not do anything for non-"no-map" regions, as memblock
> explicitly allows reserved regions to overlap, and the commit
> that this fixes removed the check for that precise reason.
>
> [ qperret: fixed conflicts caused by the usage of memblock_mark_nomap ]
>
> Fixes: 094cb98179f19b7 ("of/fdt: memblock_reserve /memreserve/ regions in the case of partial overlap")
> Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
> Reviewed-by: Stephen Boyd <swboyd@chromium.org>
> Signed-off-by: Quentin Perret <qperret@google.com>
> ---
> drivers/of/fdt.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
Applied, thanks!
next prev parent reply other threads:[~2021-01-15 17:31 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-15 11:45 [PATCH 0/2] fdt: A couple of no-map fixes Quentin Perret
2021-01-15 11:45 ` [PATCH 1/2] fdt: Properly handle "no-map" field in the memory region Quentin Perret
2021-01-15 17:29 ` Rob Herring
2021-01-15 11:45 ` [PATCH 2/2] of/fdt: Make sure no-map does not remove already reserved regions Quentin Perret
2021-01-15 17:30 ` Rob Herring [this message]
2021-01-16 0:30 ` Nicolas Boichat
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