From: Tiezhu Yang yangtiezhu@loongson.cn
[ Upstream commit 269b3a9ac538c4ae87f84be640b9fa89914a2489 ]
In the current code, if CONFIG_SWIOTLB is set, when failed to get IO TLB memory from the low pages by plat_swiotlb_setup(), it may lead to the boot process failed with kernel panic.
(1) On the Loongson and SiByte platform arch/mips/loongson64/dma.c arch/mips/sibyte/common/dma.c void __init plat_swiotlb_setup(void) { swiotlb_init(1); }
kernel/dma/swiotlb.c void __init swiotlb_init(int verbose) { ... vstart = memblock_alloc_low(PAGE_ALIGN(bytes), PAGE_SIZE); if (vstart && !swiotlb_init_with_tbl(vstart, io_tlb_nslabs, verbose)) return; ... pr_warn("Cannot allocate buffer"); no_iotlb_memory = true; }
phys_addr_t swiotlb_tbl_map_single() { ... if (no_iotlb_memory) panic("Can not allocate SWIOTLB buffer earlier ..."); ... }
(2) On the Cavium OCTEON platform arch/mips/cavium-octeon/dma-octeon.c void __init plat_swiotlb_setup(void) { ... octeon_swiotlb = memblock_alloc_low(swiotlbsize, PAGE_SIZE); if (!octeon_swiotlb) panic("%s: Failed to allocate %zu bytes align=%lx\n", __func__, swiotlbsize, PAGE_SIZE); ... }
Because IO_TLB_DEFAULT_SIZE is 64M, if the rest size of low memory is less than 64M when call plat_swiotlb_setup(), we can easily reproduce the panic case.
In order to reduce the possibility of kernel panic when failed to get IO TLB memory under CONFIG_SWIOTLB, it is better to allocate low memory as small as possible before plat_swiotlb_setup(), so make sparse_init() using top-down allocation.
Reported-by: Juxin Gao gaojuxin@loongson.cn Co-developed-by: Juxin Gao gaojuxin@loongson.cn Signed-off-by: Juxin Gao gaojuxin@loongson.cn Signed-off-by: Tiezhu Yang yangtiezhu@loongson.cn Signed-off-by: Thomas Bogendoerfer tsbogend@alpha.franken.de Signed-off-by: Sasha Levin sashal@kernel.org --- arch/mips/kernel/setup.c | 10 ++++++++++ 1 file changed, 10 insertions(+)
diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c index 05ed4ed411c7..abd7ee9e90ab 100644 --- a/arch/mips/kernel/setup.c +++ b/arch/mips/kernel/setup.c @@ -911,7 +911,17 @@ static void __init arch_mem_init(char **cmdline_p) BOOTMEM_DEFAULT); #endif device_tree_init(); + + /* + * In order to reduce the possibility of kernel panic when failed to + * get IO TLB memory under CONFIG_SWIOTLB, it is better to allocate + * low memory as small as possible before plat_swiotlb_setup(), so + * make sparse_init() using top-down allocation. + */ + memblock_set_bottom_up(false); sparse_init(); + memblock_set_bottom_up(true); + plat_swiotlb_setup();
dma_contiguous_reserve(PFN_PHYS(max_low_pfn));