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SubjectRe: [PATCH v3 3/4] arm64: kdump: support more than one crash kernel regions
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Hi Mike,

This overall looks well.
Replacing memblock_cap_memory_range() with memblock_cap_memory_ranges() was what i wanted
to do in v1, sorry for don't express that clearly.

But there are some issues as below. After fixing this, it can work correctly.

On 2019/4/10 21:09, Mike Rapoport wrote:
> 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]>
>>
>> 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];
>
> I only now noticed that fdt_enforce_memory_region() uses memblock_region to
> pass the ranges around. If we'd switch to memblock_type instead, the
> implementation of memblock_cap_memory_ranges() would be really
> straightforward. Can you check if the below patch works for you?
>
>>From e476d584098e31273af573e1a78e308880c5cf28 Mon Sep 17 00:00:00 2001
> From: Mike Rapoport <rppt@linux.ibm.com>
> Date: Wed, 10 Apr 2019 16:02:32 +0300
> Subject: [PATCH] memblock: extend memblock_cap_memory_range to multiple ranges
>
> The memblock_cap_memory_range() removes all the memory except the range
> passed to it. Extend this function to recieve memblock_type with the
> regions that should be kept. This allows switching to simple iteration over
> memblock arrays with 'for_each_mem_range' to remove the unneeded memory.
>
> Enable use of this function in arm64 for reservation of multile regions for
> the crash kernel.
>
> Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
> ---
> arch/arm64/mm/init.c | 34 ++++++++++++++++++++++++----------
> include/linux/memblock.h | 2 +-
> mm/memblock.c | 45 ++++++++++++++++++++++-----------------------
> 3 files changed, 47 insertions(+), 34 deletions(-)
>
>
> -void __init memblock_cap_memory_range(phys_addr_t base, phys_addr_t size)
> +void __init memblock_cap_memory_ranges(struct memblock_type *regions_to_keep)
> {
> - int start_rgn, end_rgn;
> - int i, ret;
> -
> - if (!size)
> - return;
> -
> - ret = memblock_isolate_range(&memblock.memory, base, size,
> - &start_rgn, &end_rgn);
> - if (ret)
> - return;
> -
> - /* remove all the MAP regions */
> - for (i = memblock.memory.cnt - 1; i >= end_rgn; i--)
> - if (!memblock_is_nomap(&memblock.memory.regions[i]))
> - memblock_remove_region(&memblock.memory, i);
> + phys_addr_t start, end;
> + u64 i;
>
> - for (i = start_rgn - 1; i >= 0; i--)
> - if (!memblock_is_nomap(&memblock.memory.regions[i]))
> - memblock_remove_region(&memblock.memory, i);
> + /* truncate memory while skipping NOMAP regions */
> + for_each_mem_range(i, &memblock.memory, regions_to_keep, NUMA_NO_NODE,
> + MEMBLOCK_NONE, &start, &end, NULL)
> + memblock_remove(start, end);

1. use memblock_remove(start, size) instead of memblock_remove(start, end).

2. There is a another hidden issue. We couldn't mix __next_mem_range()(called by for_each_mem_range) operation
with remove operation because __next_mem_range() records the index of last time. If we do remove between
__next_mem_range(), the index may be mess.

Therefore, we could do remove operation after for_each_mem_range like this, solution A:
void __init memblock_cap_memory_ranges(struct memblock_type *regions_to_keep)
{
- phys_addr_t start, end;
- u64 i;
+ phys_addr_t start[INIT_MEMBLOCK_RESERVED_REGIONS * 2];
+ phys_addr_t end[INIT_MEMBLOCK_RESERVED_REGIONS * 2];
+ u64 i, nr = 0;

/* truncate memory while skipping NOMAP regions */
for_each_mem_range(i, &memblock.memory, regions_to_keep, NUMA_NO_NODE,
- MEMBLOCK_NONE, &start, &end, NULL)
- memblock_remove(start, end);
+ MEMBLOCK_NONE, &start[nr], &end[nr], NULL)
+ nr++;
+ for (i = 0; i < nr; i++)
+ memblock_remove(start[i], end[i] - start[i]);

/* truncate the reserved regions */
+ nr = 0;
for_each_mem_range(i, &memblock.reserved, regions_to_keep, NUMA_NO_NODE,
- MEMBLOCK_NONE, &start, &end, NULL)
- memblock_remove_range(&memblock.reserved, start, end);
+ MEMBLOCK_NONE, &start[nr], &end[nr], NULL)
+ nr++;
+ for (i = 0; i < nr; i++)
+ memblock_remove_range(&memblock.reserved, start[i],
+ end[i] - start[i]);
}

But a warning occurs when compiling:
CALL scripts/atomic/check-atomics.sh
CALL scripts/checksyscalls.sh
CHK include/generated/compile.h
CC mm/memblock.o
mm/memblock.c: In function ‘memblock_cap_memory_ranges’:
mm/memblock.c:1635:1: warning: the frame size of 36912 bytes is larger than 2048 bytes [-Wframe-larger-than=]
}

another solution is my implementation in v1, solution B:
+void __init memblock_cap_memory_ranges(struct memblock_type *regions_to_keep)
+{
+ int start_rgn[INIT_MEMBLOCK_REGIONS], end_rgn[INIT_MEMBLOCK_REGIONS];
+ int i, j, ret, nr = 0;
+ memblock_region *regs = regions_to_keep->regions;
+
+ nr = regions_to_keep -> cnt;
+ 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 - 1].base + regs[i - 1].size,
+ 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);
+}

solution A: phys_addr_t start[INIT_MEMBLOCK_RESERVED_REGIONS * 2];
phys_addr_t end[INIT_MEMBLOCK_RESERVED_REGIONS * 2];
start, end is physical addr

solution B: int start_rgn[INIT_MEMBLOCK_REGIONS], end_rgn[INIT_MEMBLOCK_REGIONS];
start_rgn, end_rgn is rgn index

Solution B do less remove operations and with no warning comparing to solution A.
I think solution B is better, could you give some suggestions?

>
> /* truncate the reserved regions */
> - memblock_remove_range(&memblock.reserved, 0, base);
> - memblock_remove_range(&memblock.reserved,
> - base + size, PHYS_ADDR_MAX);
> + for_each_mem_range(i, &memblock.reserved, regions_to_keep, NUMA_NO_NODE,
> + MEMBLOCK_NONE, &start, &end, NULL)
> + memblock_remove_range(&memblock.reserved, start, end);

There are the same issues as above.

> }
>
> void __init memblock_mem_limit_remove_map(phys_addr_t limit)
> {
> + struct memblock_region rgn = {
> + .base = 0,
> + };
> +
> + struct memblock_type region_to_keep = {
> + .cnt = 1,
> + .max = 1,
> + .regions = &rgn,
> + };
> +
> phys_addr_t max_addr;
>
> if (!limit)
> @@ -1646,7 +1644,8 @@ void __init memblock_mem_limit_remove_map(phys_addr_t limit)
> if (max_addr == PHYS_ADDR_MAX)
> return;
>
> - memblock_cap_memory_range(0, max_addr);
> + region_to_keep.regions[0].size = max_addr;
> + memblock_cap_memory_ranges(&region_to_keep);
> }
>
> static int __init_memblock memblock_search(struct memblock_type *type, phys_addr_t addr)
>

Thanks,
Chen Zhou

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