On Mon, May 13, 2019 at 07:14:32PM +0800, Hsin-Yi Wang wrote: > 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'm not sure if early console is available at the time kaslr_early_init() is called, but if yes, running with memblock=debug may shed some light. > I didn't trace the real reason causing this. But in this case, maybe > don't call memblock_reserve() in kaslr? My concern that this uncovered a real bug which might hit us later. > [1] > [ 0.000000] WARNING: CPU: 0 PID: 0 at > /mnt/host/source/src/third_party/kernel/v4.19/mm/memblock.c:583 > memblock_add_range+0x1bc/0x1c8 > [ 0.000000] Modules linked in: > [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.19.38 #125 > [ 0.000000] pstate: 600001c5 (nZCv dAIF -PAN -UAO) > [ 0.000000] pc : memblock_add_range+0x1bc/0x1c8 > [ 0.000000] lr : memblock_add_range+0x30/0x1c8 > [ 0.000000] sp : ffffff9b5e203e80 > [ 0.000000] x29: ffffff9b5e203ed0 x28: 0000000040959324 > [ 0.000000] x27: 0000000040080000 x26: 0000000000080000 > [ 0.000000] x25: 0000000080127e4b x24: 0000000000000000 > [ 0.000000] x23: 0000001b55000000 x22: 000000000001152b > [ 0.000000] x21: 000000005f800000 x20: 0000000000000000 > [ 0.000000] x19: ffffff9b5e24bf00 x18: 00000000ffffffb8 > [ 0.000000] x17: 000000000000003c x16: ffffffbefea00000 > [ 0.000000] x15: ffffffbefea00000 x14: ffffff9b5e3c17d8 > [ 0.000000] x13: 00e8000000000713 x12: 0000000000000000 > [ 0.000000] x11: ffffffbefea00000 x10: 00e800005f800710 > [ 0.000000] x9 : 000000000001152b x8 : ffffff9b5e365690 > [ 0.000000] x7 : 6f20646573616228 x6 : 0000000000000002 > [ 0.000000] x5 : 0000000000000000 x4 : 0000000000000000 > [ 0.000000] x3 : 0000000000200000 x2 : 000000000001152b > [ 0.000000] x1 : 000000005f800000 x0 : ffffff9b5e24bf00 > [ 0.000000] Call trace: > [ 0.000000] memblock_add_range+0x1bc/0x1c8 > [ 0.000000] memblock_reserve+0x60/0xac > [ 0.000000] fixmap_remap_fdt+0x4c/0x78 > [ 0.000000] setup_machine_fdt+0x64/0xfc > [ 0.000000] setup_arch+0x68/0x1e0 > [ 0.000000] start_kernel+0x68/0x380 > -- Sincerely yours, Mike.
