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Date: Fri, 7 Jan 2022 17:32:20 -0600 From: Rob Herring <robh@...nel.org> To: Stephen Boyd <swboyd@...omium.org> Cc: devicetree@...r.kernel.org, Quentin Perret <qperret@...gle.com>, Rob Herring <robh+dt@...nel.org>, Jan Kiszka <jan.kiszka@...mens.com>, linux-kernel@...r.kernel.org, Nicolas Boichat <drinkcat@...omium.org>, Mike Rapoport <rppt@...nel.org>, Douglas Anderson <dianders@...omium.org> Subject: Re: [PATCH v4] of/fdt: Don't worry about non-memory region overlap for no-map On Fri, 07 Jan 2022 11:42:32 -0800, Stephen Boyd wrote: > In commit 8a5a75e5e9e5 ("of/fdt: Make sure no-map does not remove > already reserved regions") we returned -EBUSY when trying to mark > regions as no-map when they intersect with reserved memory. The goal was > to find bad no-map reserved memory DT nodes that would unmap the kernel > text/data sections. > > The problem is the reserved memory check will still trigger if the DT > has a /memreserve/ that completely subsumes the no-map memory carveouts > in the reserved memory node _and_ that region is also not part of the > memory reg property. For example in sc7180.dtsi we have the following > reserved-memory and memory node: > > memory@...00000 { > /* We expect the bootloader to fill in the size */ > reg = <0 0x80000000 0 0>; > }; > > smem_mem: memory@...00000 { > reg = <0x0 0x80900000 0x0 0x200000>; > no-map; > }; > > and the memreserve filled in by the bootloader is > > /memreserve/ 0x80800000 0x400000; > > while the /memory node is transformed into > > memory@...00000 { > /* The bootloader fills in the size, and adds another region */ > reg = <0 0x80000000 0 0x00800000>, > <0 0x80c00000 0 0x7f200000>; > }; > > The smem region is doubly reserved via /memreserve/ and by not being > part of the /memory reg property. This leads to the following warning > printed at boot. > > OF: fdt: Reserved memory: failed to reserve memory for node 'memory@...00000': base 0x0000000080900000, size 2 MiB > > Otherwise nothing really goes wrong because the smem region is not going > to be mapped by the kernel's direct linear mapping given that it isn't > part of the memory node. Therefore, let's only consider this to be a > problem if we're trying to mark a region as no-map and it is actually > memory that we're intending to keep out of the kernel's direct mapping > but it's already been reserved. > > Acked-by: Mike Rapoport <rppt@...nel.org> > Cc: Douglas Anderson <dianders@...omium.org> > Cc: Nicolas Boichat <drinkcat@...omium.org> > Cc: Quentin Perret <qperret@...gle.com> > Cc: Jan Kiszka <jan.kiszka@...mens.com> > Fixes: 8a5a75e5e9e5 ("of/fdt: Make sure no-map does not remove already reserved regions") > Signed-off-by: Stephen Boyd <swboyd@...omium.org> > --- > > Changes from v3 (https://lore.kernel.org/r/20211215195354.634746-1-swboyd@chromium.org): > * Even more details in commit text > > Changes from v2 (https://lore.kernel.org/r/20211215072011.496998-1-swboyd@chromium.org): > * More details in commit text > > Changes from v1 (https://lore.kernel.org/r/20210520012731.3731314-1-swboyd@chromium.org): > * Use memblock_overlaps_region instead of memblock_is_region_memory() > * Add more details to commit text > > drivers/of/fdt.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > Applied, thanks!
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