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Date: Sat, 16 Jan 2021 08:30:21 +0800 From: Nicolas Boichat <drinkcat@...omium.org> To: Rob Herring <robh@...nel.org> Cc: Quentin Perret <qperret@...gle.com>, Rob Herring <robh+dt@...nel.org>, Devicetree List <devicetree@...r.kernel.org>, Florian Fainelli <f.fainelli@...il.com>, Stephen Boyd <swboyd@...omium.org>, KarimAllah Ahmed <karahmed@...zon.de>, kernel-team@...roid.com, Frank Rowand <frowand.list@...il.com>, lkml <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 2/2] of/fdt: Make sure no-map does not remove already reserved regions On Sat, Jan 16, 2021 at 1:30 AM Rob Herring <robh@...nel.org> wrote: > > On Fri, 15 Jan 2021 11:45:44 +0000, Quentin Perret wrote: > > From: Nicolas Boichat <drinkcat@...omium.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@...omium.org> > > Reviewed-by: Stephen Boyd <swboyd@...omium.org> > > Signed-off-by: Quentin Perret <qperret@...gle.com> > > --- > > drivers/of/fdt.c | 10 +++++++++- > > 1 file changed, 9 insertions(+), 1 deletion(-) > > Thanks for picking up this old patch Quentin ,-) > Applied, thanks!
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