linux-kernel - Re: [PATCH v2 5/5] RISC-V: Fix memory reservation in setup

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Message-Id: <20190323154447.GB25149@rapoport-lnx>
Date:   Sat, 23 Mar 2019 17:44:47 +0200
From:   Mike Rapoport <rppt@...ux.ibm.com>
To:     Anup Patel <Anup.Patel@....com>
Cc:     Palmer Dabbelt <palmer@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Atish Patra <Atish.Patra@....com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Christoph Hellwig <hch@...radead.org>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 5/5] RISC-V: Fix memory reservation in setup_bootmem()

On Thu, Mar 21, 2019 at 09:47:58AM +0000, Anup Patel 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>
> ---
>  arch/riscv/mm/init.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 2e2f2567964c..99b42380d17d 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -18,6 +18,8 @@
>  #include <asm/pgtable.h>
>  #include <asm/io.h>
>  
> +extern char _start[];
> +
>  static void __init zone_sizes_init(void)
>  {
>  	unsigned long max_zone_pfns[MAX_NR_ZONES] = { 0, };
> @@ -93,15 +95,17 @@ void __init setup_bootmem(void)
>  
>  	/* Find the memory region containing the kernel */
>  	for_each_memblock(memory, reg) {
> -		phys_addr_t vmlinux_end = __pa(_end);
> +		phys_addr_t vmlinux_end = __pa(&_end);
> +		phys_addr_t vmlinux_start = __pa(&_start);
>  		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
> +			 * Reserve from the start of the kernel to the end of
>  			 * the kernel
>  			 */
> -			memblock_reserve(reg->base, vmlinux_end - reg->base);
> +			memblock_reserve(vmlinux_start,
> +					 vmlinux_end - vmlinux_start);

Sorry for misleading you here, but this can be done outside the loop as
well as the calculation of vmlinux_{start,end}.

>  			mem_size = min(reg->size, (phys_addr_t)-PAGE_OFFSET);
>  		}
>  	}
> @@ -177,7 +181,6 @@ struct mapping_ops {
>  
>  static inline void *__load_addr(void *ptr, uintptr_t load_pa)
>  {
> -	extern char _start;
>  	uintptr_t va = (uintptr_t)ptr;
>  	uintptr_t sz = (uintptr_t)(&_end) - (uintptr_t)(&_start);
>  
> -- 
> 2.17.1
> 

-- 
Sincerely yours,
Mike.