linux-kernel - Re: [PATCH 4/4] riscv: Parse all memory blocks to remove unusable memory

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Message-ID: <mhng-ab4785af-26a2-4494-81f7-b0c206711515@palmerdabbelt-glaptop1>
Date:   Fri, 24 Jul 2020 22:12:42 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     Atish Patra <Atish.Patra@....com>
CC:     linux-kernel@...r.kernel.org, Atish Patra <Atish.Patra@....com>,
        aou@...s.berkeley.edu, Anup Patel <Anup.Patel@....com>,
        greentime.hu@...ive.com, linux-riscv@...ts.infradead.org,
        Paul Walmsley <paul.walmsley@...ive.com>, sudeep.holla@....com,
        vincent.chen@...ive.com, zong.li@...ive.com
Subject:     Re: [PATCH 4/4] riscv: Parse all memory blocks to remove unusable memory

On Wed, 15 Jul 2020 16:30:09 PDT (-0700), Atish Patra wrote:
> Currently, maximum physical memory allowed is equal to -PAGE_OFFSET.
> That's why we remove any memory blocks spanning beyond that size. However,
> it is done only for memblock containing linux kernel which will not work
> if there are multiple memblocks.
>
> Process all memory blocks to figure out how much memory needs to be removed
> and remove at the end instead of updating the memblock list in place.
>
> Signed-off-by: Atish Patra <atish.patra@....com>
> ---
>  arch/riscv/mm/init.c | 31 +++++++++++++++++--------------
>  1 file changed, 17 insertions(+), 14 deletions(-)
>
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index f818a47a72d1..79e9d55bdf1a 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -147,26 +147,29 @@ 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);
>
>  	/* Find the memory region containing the kernel */
>  	for_each_memblock(memory, reg) {
> -		phys_addr_t end = reg->base + reg->size;
> -
> -		if (reg->base <= vmlinux_start && vmlinux_end <= end) {
> -			mem_size = min(reg->size, (phys_addr_t)-PAGE_OFFSET);
> -
> -			/*
> -			 * Remove memblock from the end of usable area to the
> -			 * end of region
> -			 */
> -			if (reg->base + mem_size < end)
> -				memblock_remove(reg->base + mem_size,
> -						end - reg->base - mem_size);
> -		}
> +		end = reg->base + reg->size;
> +		if (!total_mem)
> +			mem_start = reg->base;
> +		if (reg->base <= vmlinux_start && vmlinux_end <= end)
> +			BUG_ON(reg->size == 0);
> +		total_mem = total_mem + reg->size;
>  	}
> -	BUG_ON(mem_size == 0);
> +
> +	/*
> +	 * Remove memblock from the end of usable area to the
> +	 * end of region
> +	 */
> +	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);
>
>  	/* Reserve from the start of the kernel to the end of the kernel */
>  	memblock_reserve(vmlinux_start, vmlinux_end - vmlinux_start);

Thanks, this one is also on fixes.