Re: [PATCH 2/3] arm64: kdump: support more than one crash kernel regions

Chen Zhou
2019-04-03T13:51:54Z

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,
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
>>
>