From 8f579b1c4e347b23bfa747bc2cc0a55dd1b7e5fa Mon Sep 17 00:00:00 2001 From: AKASHI Takahiro Date: Mon, 3 Apr 2017 11:24:31 +0900 Subject: [PATCH] arm64: limit memory regions based on DT property, usable-memory-range Crash dump kernel uses only a limited range of available memory as System RAM. On arm64 kdump, This memory range is advertised to crash dump kernel via a device-tree property under /chosen, linux,usable-memory-range = Crash dump kernel reads this property at boot time and calls memblock_cap_memory_range() to limit usable memory which are listed either in UEFI memory map table or "memory" nodes of a device tree blob. Signed-off-by: AKASHI Takahiro Reviewed-by: Geoff Levand Acked-by: Catalin Marinas Acked-by: Mark Rutland Reviewed-by: Ard Biesheuvel Signed-off-by: Catalin Marinas --- arch/arm64/mm/init.c | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index e19e06593e37..290794b1a0f1 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -188,10 +188,45 @@ static int __init early_mem(char *p) } early_param("mem", early_mem); +static int __init early_init_dt_scan_usablemem(unsigned long node, + const char *uname, int depth, void *data) +{ + struct memblock_region *usablemem = data; + const __be32 *reg; + int len; + + if (depth != 1 || strcmp(uname, "chosen") != 0) + return 0; + + reg = of_get_flat_dt_prop(node, "linux,usable-memory-range", &len); + if (!reg || (len < (dt_root_addr_cells + dt_root_size_cells))) + return 1; + + usablemem->base = dt_mem_next_cell(dt_root_addr_cells, ®); + usablemem->size = dt_mem_next_cell(dt_root_size_cells, ®); + + return 1; +} + +static void __init fdt_enforce_memory_region(void) +{ + struct memblock_region reg = { + .size = 0, + }; + + of_scan_flat_dt(early_init_dt_scan_usablemem, ®); + + if (reg.size) + memblock_cap_memory_range(reg.base, reg.size); +} + void __init arm64_memblock_init(void) { const s64 linear_region_size = -(s64)PAGE_OFFSET; + /* Handle linux,usable-memory-range property */ + fdt_enforce_memory_region(); + /* * Ensure that the linear region takes up exactly half of the kernel * virtual address space. This way, we can distinguish a linear address -- GitLab