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Commit 8f579b1c authored by AKASHI Takahiro's avatar AKASHI Takahiro Committed by Catalin Marinas
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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 = <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: default avatarAKASHI Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: default avatarGeoff Levand <geoff@infradead.org>
Acked-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Acked-by: default avatarMark Rutland <mark.rutland@arm.com>
Reviewed-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent c9ca9b4e

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