arm64: limit memory regions based on DT property, usable-memory-range (8f579b1c) · Commits · 戴 / test

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 = <BASE SIZE> 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 <takahiro.akashi@linaro.org> Reviewed-by:

Geoff Levand <geoff@infradead.org> Acked-by:

Catalin Marinas <catalin.marinas@arm.com> Acked-by:

Mark Rutland <mark.rutland@arm.com> Reviewed-by:

Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by:

Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/mm/init.c

+35 −0

Original line number	Diff line number	Diff line
		@@ -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, &reg);
		usablemem->size = dt_mem_next_cell(dt_root_size_cells, &reg);

		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, &reg);

		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

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