Re: [PATCH v3 3/4] arm64: kdump: support more than one crash kernel regions

[Mike Rapoport]

Hi,

On Tue, Apr 09, 2019 at 06:28:18PM +0800, Chen Zhou wrote:
> After commit (arm64: kdump: support reserving crashkernel above 4G),
> there may be two crash kernel regions, one is below 4G, the other is
> above 4G.
> 
> Crash dump kernel reads more than one crash kernel regions via a dtb
> property under node /chosen,
> linux,usable-memory-range = <BASE1 SIZE1 [BASE2 SIZE2]>
> 
> Signed-off-by: Chen Zhou <chenzhou10@xxxxxxxxxx>
> ---
>  arch/arm64/mm/init.c     | 66 ++++++++++++++++++++++++++++++++++++++++--------
>  include/linux/memblock.h |  6 +++++
>  mm/memblock.c            |  7 ++---
>  3 files changed, 66 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 3bebddf..0f18665 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -65,6 +65,11 @@ phys_addr_t arm64_dma_phys_limit __ro_after_init;
>  
>  #ifdef CONFIG_KEXEC_CORE
>  
> +/* at most two crash kernel regions, low_region and high_region */
> +#define CRASH_MAX_USABLE_RANGES	2
> +#define LOW_REGION_IDX			0
> +#define HIGH_REGION_IDX			1
> +
>  /*
>   * reserve_crashkernel() - reserves memory for crash kernel
>   *
> @@ -297,8 +302,8 @@ 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;
> +	const __be32 *reg, *endp;
> +	int len, nr = 0;
>  
>  	if (depth != 1 || strcmp(uname, "chosen") != 0)
>  		return 0;
> @@ -307,22 +312,63 @@ static int __init early_init_dt_scan_usablemem(unsigned long node,
>  	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);
> +	endp = reg + (len / sizeof(__be32));
> +	while ((endp - reg) >= (dt_root_addr_cells + dt_root_size_cells)) {
> +		usablemem[nr].base = dt_mem_next_cell(dt_root_addr_cells, &reg);
> +		usablemem[nr].size = dt_mem_next_cell(dt_root_size_cells, &reg);
> +
> +		if (++nr >= CRASH_MAX_USABLE_RANGES)
> +			break;
> +	}
>  
>  	return 1;
>  }
>  
>  static void __init fdt_enforce_memory_region(void)
>  {
> -	struct memblock_region reg = {
> -		.size = 0,
> -	};
> +	int i, cnt = 0;
> +	struct memblock_region regs[CRASH_MAX_USABLE_RANGES];

I only now noticed that fdt_enforce_memory_region() uses memblock_region to
pass the ranges around. If we'd switch to memblock_type instead, the
implementation of memblock_cap_memory_ranges() would be really
straightforward. Can you check if the below patch works for you?