linux-kernel - Re: [PATCH v3 2/4] RISC-V: Fix memory reservation in setup

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Date:   Wed, 24 Apr 2019 14:06:47 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...ive.com>
To:     Anup.Patel@....com
CC:     aou@...s.berkeley.edu, Atish Patra <Atish.Patra@....com>,
        Christoph Hellwig <hch@...radead.org>,
        Paul Walmsley <paul.walmsley@...ive.com>, rppt@...ux.ibm.com,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Anup.Patel@....com
Subject:     Re: [PATCH v3 2/4] RISC-V: Fix memory reservation in setup_bootmem()

On Mon, 25 Mar 2019 02:23:09 PDT (-0700), Anup.Patel@....com wrote:
> Currently, the setup_bootmem() reserves memory from RAM start to the
> kernel end. This prevents us from exploring ways to use the RAM below
> (or before) the kernel start hence this patch updates setup_bootmem()
> to only reserve memory from the kernel start to the kernel end.
>
> Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
> Signed-off-by: Anup Patel <anup.patel@....com>
> Reviewed-by: Christoph Hellwig <hch@....de>
> ---
>  arch/riscv/mm/init.c | 17 ++++++++---------
>  1 file changed, 8 insertions(+), 9 deletions(-)
>
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 8cf9ff1f9058..3e66b7cb3a61 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -29,6 +29,8 @@ unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
>  							__page_aligned_bss;
>  EXPORT_SYMBOL(empty_zero_page);
>  
> +extern char _start[];
> +
>  static void __init zone_sizes_init(void)
>  {
>  	unsigned long max_zone_pfns[MAX_NR_ZONES] = { 0, };
> @@ -108,23 +110,21 @@ void __init setup_bootmem(void)
>  {
>  	struct memblock_region *reg;
>  	phys_addr_t mem_size = 0;
> +	phys_addr_t vmlinux_end = __pa(&_end);
> +	phys_addr_t vmlinux_start = __pa(&_start);
>  
>  	/* Find the memory region containing the kernel */
>  	for_each_memblock(memory, reg) {
> -		phys_addr_t vmlinux_end = __pa(_end);
>  		phys_addr_t end = reg->base + reg->size;
>  
> -		if (reg->base <= vmlinux_end && vmlinux_end <= end) {
> -			/*
> -			 * Reserve from the start of the region to the end of
> -			 * the kernel
> -			 */
> -			memblock_reserve(reg->base, vmlinux_end - reg->base);
> +		if (reg->base <= vmlinux_end && vmlinux_end <= end)
>  			mem_size = min(reg->size, (phys_addr_t)-PAGE_OFFSET);
> -		}
>  	}
>  	BUG_ON(mem_size == 0);
>  
> +	/* Reserve from the start of the kernel to the end of the kernel */
> +	memblock_reserve(vmlinux_start, vmlinux_end - vmlinux_start);
> +
>  	set_max_mapnr(PFN_DOWN(mem_size));
>  	max_low_pfn = PFN_DOWN(memblock_end_of_DRAM());
>  
> @@ -196,7 +196,6 @@ void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
>   */
>  asmlinkage void __init setup_vm(void)
>  {
> -	extern char _start;
>  	uintptr_t i;
>  	uintptr_t pa = (uintptr_t) &_start;
>  	pgprot_t prot = __pgprot(pgprot_val(PAGE_KERNEL) | _PAGE_EXEC);
> -- 
> 2.17.1

I've already merged your first patch for 5.1, but I'm going through and
collecting 5.2 patches now and it appears this has a conflict.  Do you mind
re-submitting the patch set against rc6?