Quoting Hsin-Yi Wang (2019-05-13 04:14:32) > On Mon, May 13, 2019 at 4:59 PM Mike Rapoport <rppt@xxxxxxxxxxxxx> wrote: > > > > > This makes the fdt mapped without the call to meblock_reserve(fdt) which > > makes the fdt memory available for memblock allocations. > > > > Chances that is will be actually allocated are small, but you know, things > > happen. > > > > IMHO, instead of calling directly __fixmap_remap_fdt() it would be better > > to add pgprot parameter to fixmap_remap_fdt(). Then here and in kaslr.c it > > can be called with PAGE_KERNEL and below with PAGE_KERNEL_RO. > > > > There is no problem to call memblock_reserve() for the same area twice, > > it's essentially a NOP. > > > Thanks for the suggestion. Will update fixmap_remap_fdt() in next patch. > > However, I tested on some arm64 platform, if we also call > memblock_reserve() in kaslr.c, would cause warning[1] when > memblock_reserve() is called again in setup_machine_fdt(). The warning > comes from https://elixir.bootlin.com/linux/latest/source/mm/memblock.c#L601 > ``` > if (type->regions[0].size == 0) { > WARN_ON(type->cnt != 1 || type->total_size); > ... > ``` > > Call memblock_reserve() multiple times after setup_machine_fdt() > doesn't have such warning though. > > I didn't trace the real reason causing this. But in this case, maybe > don't call memblock_reserve() in kaslr? > Why not just have fixmap_remap_fdt() that maps it as RW and reserves memblock once, and then call __fixmap_remap_fdt() with RO after early_init_dt_scan() or unflatten_device_tree() is called? Why the desire to call memblock_reserve() twice or even three times?
