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Date:   Sun, 14 Apr 2019 15:13:15 +0300
From:   Mike Rapoport <rppt@linux.ibm.com>
To:     Chen Zhou <chenzhou10@huawei.com>
Cc:     tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
        ebiederm@xmission.com, catalin.marinas@arm.com,
        will.deacon@arm.com, akpm@linux-foundation.org,
        ard.biesheuvel@linaro.org, horms@verge.net.au,
        takahiro.akashi@linaro.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, kexec@lists.infradead.org,
        linux-mm@kvack.org, wangkefeng.wang@huawei.com
Subject: Re: [PATCH v3 3/4] arm64: kdump: support more than one crash kernel
 regions
References: <20190409102819.121335-1-chenzhou10@huawei.com>
 <20190409102819.121335-4-chenzhou10@huawei.com>
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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]>

Somehow I've missed that previously, but how is this supposed to work on
EFI systems?
 
> Signed-off-by: Chen Zhou <chenzhou10@huawei.com>
> ---
>  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];
> +
> +	memset(regs, 0, sizeof(regs));
> +	of_scan_flat_dt(early_init_dt_scan_usablemem, regs);
> +
> +	for (i = 0; i < CRASH_MAX_USABLE_RANGES; i++)
> +		if (regs[i].size)
> +			cnt++;
> +		else
> +			break;
> +
> +	if (cnt - 1 == LOW_REGION_IDX)
> +		memblock_cap_memory_range(regs[LOW_REGION_IDX].base,
> +				regs[LOW_REGION_IDX].size);
> +	else if (cnt - 1 == HIGH_REGION_IDX) {
> +		/*
> +		 * Two crash kernel regions, cap the memory range
> +		 * [regs[LOW_REGION_IDX].base, regs[HIGH_REGION_IDX].end]
> +		 * and then remove the memory range in the middle.
> +		 */
> +		int start_rgn, end_rgn, i, ret;
> +		phys_addr_t mid_base, mid_size;
> +
> +		mid_base = regs[LOW_REGION_IDX].base + regs[LOW_REGION_IDX].size;
> +		mid_size = regs[HIGH_REGION_IDX].base - mid_base;
> +		ret = memblock_isolate_range(&memblock.memory, mid_base,
> +				mid_size, &start_rgn, &end_rgn);
>  
> -	of_scan_flat_dt(early_init_dt_scan_usablemem, &reg);
> +		if (ret)
> +			return;
>  
> -	if (reg.size)
> -		memblock_cap_memory_range(reg.base, reg.size);
> +		memblock_cap_memory_range(regs[LOW_REGION_IDX].base,
> +				regs[HIGH_REGION_IDX].base -
> +				regs[LOW_REGION_IDX].base +
> +				regs[HIGH_REGION_IDX].size);
> +		for (i = end_rgn - 1; i >= start_rgn; i--) {
> +			if (!memblock_is_nomap(&memblock.memory.regions[i]))
> +				memblock_remove_region(&memblock.memory, i);
> +		}
> +		memblock_remove_range(&memblock.reserved, mid_base,
> +				mid_base + mid_size);
> +	}
>  }
>  
>  void __init arm64_memblock_init(void)
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index 294d5d8..787d252 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -110,9 +110,15 @@ void memblock_discard(void);
>  
>  phys_addr_t memblock_find_in_range(phys_addr_t start, phys_addr_t end,
>  				   phys_addr_t size, phys_addr_t align);
> +void memblock_remove_region(struct memblock_type *type, unsigned long r);
>  void memblock_allow_resize(void);
>  int memblock_add_node(phys_addr_t base, phys_addr_t size, int nid);
>  int memblock_add(phys_addr_t base, phys_addr_t size);
> +int memblock_isolate_range(struct memblock_type *type,
> +					phys_addr_t base, phys_addr_t size,
> +					int *start_rgn, int *end_rgn);
> +int memblock_remove_range(struct memblock_type *type,
> +					phys_addr_t base, phys_addr_t size);
>  int memblock_remove(phys_addr_t base, phys_addr_t size);
>  int memblock_free(phys_addr_t base, phys_addr_t size);
>  int memblock_reserve(phys_addr_t base, phys_addr_t size);
> diff --git a/mm/memblock.c b/mm/memblock.c
> index e7665cf..1846e2d 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -357,7 +357,8 @@ phys_addr_t __init_memblock memblock_find_in_range(phys_addr_t start,
>  	return ret;
>  }
>  
> -static void __init_memblock memblock_remove_region(struct memblock_type *type, unsigned long r)
> +void __init_memblock memblock_remove_region(struct memblock_type *type,
> +					unsigned long r)
>  {
>  	type->total_size -= type->regions[r].size;
>  	memmove(&type->regions[r], &type->regions[r + 1],
> @@ -724,7 +725,7 @@ int __init_memblock memblock_add(phys_addr_t base, phys_addr_t size)
>   * Return:
>   * 0 on success, -errno on failure.
>   */
> -static int __init_memblock memblock_isolate_range(struct memblock_type *type,
> +int __init_memblock memblock_isolate_range(struct memblock_type *type,
>  					phys_addr_t base, phys_addr_t size,
>  					int *start_rgn, int *end_rgn)
>  {
> @@ -784,7 +785,7 @@ static int __init_memblock memblock_isolate_range(struct memblock_type *type,
>  	return 0;
>  }
>  
> -static int __init_memblock memblock_remove_range(struct memblock_type *type,
> +int __init_memblock memblock_remove_range(struct memblock_type *type,
>  					  phys_addr_t base, phys_addr_t size)
>  {
>  	int start_rgn, end_rgn;
> -- 
> 2.7.4
> 

-- 
Sincerely yours,
Mike.