From: Stephen Boyd swboyd@chromium.org
[ Upstream commit da17d6905d29ddcdc04b2fdc37ed8cf1e8437cc8 ]
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@80000000 { /* We expect the bootloader to fill in the size */ reg = <0 0x80000000 0 0>; };
smem_mem: memory@80900000 { 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@80000000 { /* 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@80900000': 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@kernel.org Cc: Douglas Anderson dianders@chromium.org Cc: Nicolas Boichat drinkcat@chromium.org Cc: Quentin Perret qperret@google.com Cc: Jan Kiszka jan.kiszka@siemens.com Fixes: 8a5a75e5e9e5 ("of/fdt: Make sure no-map does not remove already reserved regions") Signed-off-by: Stephen Boyd swboyd@chromium.org Signed-off-by: Rob Herring robh@kernel.org Link: https://lore.kernel.org/r/20220107194233.2793146-1-swboyd@chromium.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/of/fdt.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c index 32e5e782d43da..59a7a9ee58ef7 100644 --- a/drivers/of/fdt.c +++ b/drivers/of/fdt.c @@ -482,9 +482,11 @@ static int __init early_init_dt_reserve_memory_arch(phys_addr_t base, if (nomap) { /* * If the memory is already reserved (by another region), we - * should not allow it to be marked nomap. + * should not allow it to be marked nomap, but don't worry + * if the region isn't memory as it won't be mapped. */ - if (memblock_is_region_reserved(base, size)) + if (memblock_overlaps_region(&memblock.memory, base, size) && + memblock_is_region_reserved(base, size)) return -EBUSY;
return memblock_mark_nomap(base, size);