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Date:   Thu, 4 Apr 2019 17:44:09 +0300
From:   Mike Rapoport <rppt@linux.ibm.com>
To:     Chen Zhou <chenzhou10@huawei.com>
Cc:     catalin.marinas@arm.com, will.deacon@arm.com,
        akpm@linux-foundation.org, ard.biesheuvel@linaro.org,
        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 2/3] arm64: kdump: support more than one crash kernel
 regions
References: <20190403030546.23718-1-chenzhou10@huawei.com>
 <20190403030546.23718-3-chenzhou10@huawei.com>
 <20190403112929.GA7715@rapoport-lnx>
 <f98a5559-3659-fb35-3765-15861e70a796@huawei.com>
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In-Reply-To: <f98a5559-3659-fb35-3765-15861e70a796@huawei.com>
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Message-Id: <20190404144408.GA6433@rapoport-lnx>
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Hi,

On Wed, Apr 03, 2019 at 09:51:27PM +0800, Chen Zhou wrote:
> Hi Mike,
> 
> On 2019/4/3 19:29, Mike Rapoport wrote:
> > On Wed, Apr 03, 2019 at 11:05:45AM +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@huawei.com>
> >> ---
> >>  arch/arm64/mm/init.c     | 37 +++++++++++++++++++++++++------------
> >>  include/linux/memblock.h |  1 +
> >>  mm/memblock.c            | 40 ++++++++++++++++++++++++++++++++++++++++
> >>  3 files changed, 66 insertions(+), 12 deletions(-)
> >>
> >> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> >> index ceb2a25..769c77a 100644
> >> --- a/arch/arm64/mm/init.c
> >> +++ b/arch/arm64/mm/init.c
> >> @@ -64,6 +64,8 @@ EXPORT_SYMBOL(memstart_addr);
> >>  phys_addr_t arm64_dma_phys_limit __ro_after_init;
> >>  
> >>  #ifdef CONFIG_KEXEC_CORE
> >> +# define CRASH_MAX_USABLE_RANGES        2
> >> +
> >>  static int __init reserve_crashkernel_low(void)
> >>  {
> >>  	unsigned long long base, low_base = 0, low_size = 0;
> >> @@ -346,8 +348,8 @@ 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;
> >> @@ -356,22 +358,33 @@ 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,
> >> -	};
> >> -
> >> -	of_scan_flat_dt(early_init_dt_scan_usablemem, &reg);
> >> -
> >> -	if (reg.size)
> >> -		memblock_cap_memory_range(reg.base, reg.size);
> >> +	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)
> >> +		memblock_cap_memory_ranges(regs, cnt);
> > 
> > Why not simply call memblock_cap_memory_range() for each region?
> 
> Function memblock_cap_memory_range() removes all memory type ranges except specified range.
> So if we call memblock_cap_memory_range() for each region simply, there will be no usable-memory
> on kdump capture kernel.

Thanks for the clarification.
I still think that memblock_cap_memory_ranges() is overly complex. 

How about doing something like this:

Cap the memory range for [min(regs[*].start, max(regs[*].end)] and then
removing the range in the middle?
 
> Thanks,
> Chen Zhou
> 
> > 
> >>  }
> >>  
> >>  void __init arm64_memblock_init(void)
> >> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> >> index 47e3c06..aeade34 100644
> >> --- a/include/linux/memblock.h
> >> +++ b/include/linux/memblock.h
> >> @@ -446,6 +446,7 @@ phys_addr_t memblock_start_of_DRAM(void);
> >>  phys_addr_t memblock_end_of_DRAM(void);
> >>  void memblock_enforce_memory_limit(phys_addr_t memory_limit);
> >>  void memblock_cap_memory_range(phys_addr_t base, phys_addr_t size);
> >> +void memblock_cap_memory_ranges(struct memblock_region *regs, int cnt);
> >>  void memblock_mem_limit_remove_map(phys_addr_t limit);
> >>  bool memblock_is_memory(phys_addr_t addr);
> >>  bool memblock_is_map_memory(phys_addr_t addr);
> >> diff --git a/mm/memblock.c b/mm/memblock.c
> >> index 28fa8926..1a7f4ee7c 100644
> >> --- a/mm/memblock.c
> >> +++ b/mm/memblock.c
> >> @@ -1697,6 +1697,46 @@ void __init memblock_cap_memory_range(phys_addr_t base, phys_addr_t size)
> >>  			base + size, PHYS_ADDR_MAX);
> >>  }
> >>  
> >> +void __init memblock_cap_memory_ranges(struct memblock_region *regs, int cnt)
> >> +{
> >> +	int start_rgn[INIT_MEMBLOCK_REGIONS], end_rgn[INIT_MEMBLOCK_REGIONS];
> >> +	int i, j, ret, nr = 0;
> >> +
> >> +	for (i = 0; i < cnt; i++) {
> >> +		ret = memblock_isolate_range(&memblock.memory, regs[i].base,
> >> +				regs[i].size, &start_rgn[i], &end_rgn[i]);
> >> +		if (ret)
> >> +			break;
> >> +		nr++;
> >> +	}
> >> +	if (!nr)
> >> +		return;
> >> +
> >> +	/* remove all the MAP regions */
> >> +	for (i = memblock.memory.cnt - 1; i >= end_rgn[nr - 1]; i--)
> >> +		if (!memblock_is_nomap(&memblock.memory.regions[i]))
> >> +			memblock_remove_region(&memblock.memory, i);
> >> +
> >> +	for (i = nr - 1; i > 0; i--)
> >> +		for (j = start_rgn[i] - 1; j >= end_rgn[i - 1]; j--)
> >> +			if (!memblock_is_nomap(&memblock.memory.regions[j]))
> >> +				memblock_remove_region(&memblock.memory, j);
> >> +
> >> +	for (i = start_rgn[0] - 1; i >= 0; i--)
> >> +		if (!memblock_is_nomap(&memblock.memory.regions[i]))
> >> +			memblock_remove_region(&memblock.memory, i);
> >> +
> >> +	/* truncate the reserved regions */
> >> +	memblock_remove_range(&memblock.reserved, 0, regs[0].base);
> >> +
> >> +	for (i = nr - 1; i > 0; i--)
> >> +		memblock_remove_range(&memblock.reserved,
> >> +				regs[i].base, regs[i - 1].base + regs[i - 1].size);
> >> +
> >> +	memblock_remove_range(&memblock.reserved,
> >> +			regs[nr - 1].base + regs[nr - 1].size, PHYS_ADDR_MAX);
> >> +}
> >> +
> >>  void __init memblock_mem_limit_remove_map(phys_addr_t limit)
> >>  {
> >>  	phys_addr_t max_addr;
> >> -- 
> >> 2.7.4
> >>
> > 
> 

-- 
Sincerely yours,
Mike.