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

Chen Zhou
2019-04-05T02:17:26Z

Hi Mike,

On 2019/4/4 22:44, Mike Rapoport wrote:
> 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?

Yes, that would be ok. But that would do one more memblock_cap_memory_range operation.
That is, if there are n regions, we need to do (n + 1) operations, which doesn't seem to
matter.

I agree with you, your idea is better.

Thanks,
Chen Zhou

>
>> 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
>>>>
>>>
>>
>