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SubjectRe: [PATCH v3] RISC-V: Remove any memblock representing unusable memory area
On Fri, Oct 2, 2020 at 12:36 AM Atish Patra <atish.patra@wdc.com> wrote:
>
> RISC-V limits the physical memory size by -PAGE_OFFSET. Any memory beyond
> that size from DRAM start is unusable. Just remove any memblock pointing
> to those memory region without worrying about computing the maximum size.
>
> Signed-off-by: Atish Patra <atish.patra@wdc.com>
> Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
>
> ---
> Changes from v2->v3
> Updated comment as per Mike's suggestion.
> ---
> arch/riscv/mm/init.c | 15 +++++----------
> 1 file changed, 5 insertions(+), 10 deletions(-)
>
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index ca03762a3733..564e0be677b7 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -146,8 +146,6 @@ static phys_addr_t dtb_early_pa __initdata;
> void __init setup_bootmem(void)
> {
> struct memblock_region *reg;
> - phys_addr_t mem_size = 0;
> - phys_addr_t total_mem = 0;
> phys_addr_t mem_start, end = 0;
> phys_addr_t vmlinux_end = __pa_symbol(&_end);
> phys_addr_t vmlinux_start = __pa_symbol(&_start);
> @@ -155,21 +153,18 @@ void __init setup_bootmem(void)
> /* Find the memory region containing the kernel */
> for_each_memblock(memory, reg) {
> end = reg->base + reg->size;
> - if (!total_mem)
> + if (!mem_start)
> mem_start = reg->base;
> if (reg->base <= vmlinux_start && vmlinux_end <= end)
> BUG_ON(reg->size == 0);
> - total_mem = total_mem + reg->size;
> }
>
> /*
> - * Remove memblock from the end of usable area to the
> - * end of region
> + * The maximal physical memory size is -PAGE_OFFSET.
> + * Make sure that any memory beyond mem_start + (-PAGE_OFFSET) is removed
> + * as it is unusable by kernel.
> */
> - mem_size = min(total_mem, (phys_addr_t)-PAGE_OFFSET);
> - if (mem_start + mem_size < end)
> - memblock_remove(mem_start + mem_size,
> - end - mem_start - mem_size);
> + memblock_enforce_memory_limit(mem_start - PAGE_OFFSET);
>
> /* Reserve from the start of the kernel to the end of the kernel */
> memblock_reserve(vmlinux_start, vmlinux_end - vmlinux_start);
> --
> 2.25.1
>

Looks good to me.

Reviewed-by: Anup Patel <anup@brainfault.org>

Regards,
Anup

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