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

Chen Zhou
2019-04-08T15:38:55Z

Hi Mike,

On 2019/4/8 16:39, Chen Zhou wrote:

>>>
>>> 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()?
>>
>> arm64 is the only user of both MEMBLOCK_NOMAP and memblock_cap_memory_range()
>> and I don't expect other architectures will use these interfaces.
>> It seems that capping the memory for arm64 crash kernel the way I've
>> suggested can be implemented in fdt_enforce_memory_region(). If we'd ever
>> need such functionality elsewhere or CRASH_MAX_USABLE_RANGES will need to
>> grow we'll rethink the solution.
>
> Ok, i will implement that in fdt_enforce_memory_region() in next version.
> And we will support at most two crash kernel regions now.
>
> Thanks,
> Chen Zhou
>

I implement that in fdt_enforce_memory_region() simply as below.
You have a look at if it is the way you suggested.

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index f9fa5f8..52bd69db 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
*
@@ -296,8 +301,8 @@ 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;
@@ -306,22 +311,62 @@ 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];
+
+ 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 - 1 == LOW_REGION_IDX)
+ memblock_cap_memory_range(regs[LOW_REGION_IDX].base,
+ regs[LOW_REGION_IDX].size);
+ else if (cnt - 1 == HIGH_REGION_IDX) {
+ /*
+ * Two crash kernel regions, cap the memory range
+ * [regs[LOW_REGION_IDX].base, regs[HIGH_REGION_IDX].end]
+ * and then remove the memory range in the middle.
+ */
+ int start_rgn, end_rgn, i, ret;
+ phys_addr_t mid_base, mid_size;
+
+ mid_base = regs[LOW_REGION_IDX].base + regs[LOW_REGION_IDX].size;
+ mid_size = regs[HIGH_REGION_IDX].base - mid_base;
+ ret = memblock_isolate_range(&memblock.memory, mid_base, mid_size,
+ &start_rgn, &end_rgn);

- of_scan_flat_dt(early_init_dt_scan_usablemem, &reg);
+ if (ret)
+ return;

- if (reg.size)
- memblock_cap_memory_range(reg.base, reg.size);
+ memblock_cap_memory_range(regs[LOW_REGION_IDX].base,
+ regs[HIGH_REGION_IDX].base - regs[LOW_REGION_IDX].base +
+ regs[HIGH_REGION_IDX].size);
+ for (i = end_rgn - 1; i >= start_rgn; i--) {
+ if (!memblock_is_nomap(&memblock.memory.regions[i]))
+ memblock_remove_region(&memblock.memory, i);
+ }
+ memblock_remove_range(&memblock.reserved, mid_base,
+ mid_base + mid_size);
+ }
}

void __init arm64_memblock_init(void)
diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index 294d5d8..787d252 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -110,9 +110,15 @@ void memblock_discard(void);

phys_addr_t memblock_find_in_range(phys_addr_t start, phys_addr_t end,
phys_addr_t size, phys_addr_t align);
+void memblock_remove_region(struct memblock_type *type, unsigned long r);
void memblock_allow_resize(void);
int memblock_add_node(phys_addr_t base, phys_addr_t size, int nid);
int memblock_add(phys_addr_t base, phys_addr_t size);
+int memblock_isolate_range(struct memblock_type *type,
+ phys_addr_t base, phys_addr_t size,
+ int *start_rgn, int *end_rgn);
+int memblock_remove_range(struct memblock_type *type,
+ phys_addr_t base, phys_addr_t size);
int memblock_remove(phys_addr_t base, phys_addr_t size);
int memblock_free(phys_addr_t base, phys_addr_t size);
int memblock_reserve(phys_addr_t base, phys_addr_t size);
diff --git a/mm/memblock.c b/mm/memblock.c
index e7665cf..7130c3a 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -357,7 +357,7 @@ phys_addr_t __init_memblock memblock_find_in_range(phys_addr_t start,
return ret;
}

-static void __init_memblock memblock_remove_region(struct memblock_type *type, unsigned long r)
+void __init_memblock memblock_remove_region(struct memblock_type *type, unsigned long r)
{
type->total_size -= type->regions[r].size;
memmove(&type->regions[r], &type->regions[r + 1],
@@ -724,7 +724,7 @@ int __init_memblock memblock_add(phys_addr_t base, phys_addr_t size)
* Return:
* 0 on success, -errno on failure.
*/
-static int __init_memblock memblock_isolate_range(struct memblock_type *type,
+int __init_memblock memblock_isolate_range(struct memblock_type *type,
phys_addr_t base, phys_addr_t size,
int *start_rgn, int *end_rgn)
{
@@ -784,7 +784,7 @@ static int __init_memblock memblock_isolate_range(struct memblock_type *type,
return 0;
}

-static int __init_memblock memblock_remove_range(struct memblock_type *type,
+int __init_memblock memblock_remove_range(struct memblock_type *type,
phys_addr_t base, phys_addr_t size)
{
int start_rgn, end_rgn;

Thanks,
Chen Zhou

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