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

Chen Zhou
2019-04-05T03:47:40Z

Hi Mike,

On 2019/4/5 10:17, Chen Zhou wrote:
> 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

Sorry, just ignore my previous reply, I got that wrong.

I think it carefully, we can cap the memory range for [min(regs[*].start, max(regs[*].end)]
firstly. But how to remove the middle ranges, we still can't use memblock_cap_memory_range()
directly and the extra remove operation may be complex.

For more than one regions, i think add a new memblock_cap_memory_ranges() may be better.
Besides, memblock_cap_memory_ranges() is also applicable for one region.

How about replace memblock_cap_memory_range() with memblock_cap_memory_ranges()?

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
>>>>>
>>>>
>>>
>>
>
>
> .
>