[PATCH v34 03/14] arm64: limit memory regions based on DT property, usable-memory-range

[Ard Biesheuvel]

On 28 March 2017 at 07:51, AKASHI Takahiro <takahiro.akashi at linaro.org> wrote:
> 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 at linaro.org>
> Reviewed-by: Geoff Levand <geoff at infradead.org>
> Acked-by: Catalin Marinas <catalin.marinas at arm.com>
> Acked-by: Mark Rutland <mark.rutland at arm.com>

Reviewed-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>

> ---
>  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, &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
> --
> 2.11.1
>