On 2021/12/1 6:16, Rob Herring wrote:
> On Tue, Nov 23, 2021 at 08:46:45PM +0800, Zhen Lei wrote:
>> From: Chen Zhou <chenzhou10@xxxxxxxxxx>
>>
>> When reserving crashkernel in high memory, some low memory is reserved
>> for crash dump kernel devices and never mapped by the first kernel.
>> This memory range is advertised to crash dump kernel via DT property
>> under /chosen,
>> linux,usable-memory-range = <BASE1 SIZE1 [BASE2 SIZE2]>
>>
>> We reused the DT property linux,usable-memory-range and made the low
>> memory region as the second range "BASE2 SIZE2", which keeps compatibility
>> with existing user-space and older kdump kernels.
>>
>> Crash dump kernel reads this property at boot time and call memblock_add()
>> to add the low memory region after memblock_cap_memory_range() has been
>> called.
>>
>> Signed-off-by: Chen Zhou <chenzhou10@xxxxxxxxxx>
>> Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
>> ---
>> drivers/of/fdt.c | 36 ++++++++++++++++++++++++++----------
>> 1 file changed, 26 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
>> index 37b477a51175359..1ea2a0b1657e3a9 100644
>> --- a/drivers/of/fdt.c
>> +++ b/drivers/of/fdt.c
>> @@ -967,6 +967,15 @@ static void __init early_init_dt_check_for_elfcorehdr(unsigned long node)
>>
>> static unsigned long chosen_node_offset = -FDT_ERR_NOTFOUND;
>>
>> +/*
>> + * The main usage of linux,usable-memory-range is for crash dump kernel.
>> + * Originally, the number of usable-memory regions is one. Now there may
>> + * be two regions, low region and high region.
>> + * To make compatibility with existing user-space and older kdump, the low
>> + * region is always the last range of linux,usable-memory-range if exist.
>> + */
>> +#define MAX_USABLE_RANGES 2
>> +
>> /**
>> * early_init_dt_check_for_usable_mem_range - Decode usable memory range
>> * location from flat tree
>> @@ -974,10 +983,9 @@ static unsigned long chosen_node_offset = -FDT_ERR_NOTFOUND;
>> */
>> static void __init early_init_dt_check_for_usable_mem_range(unsigned long node)
>> {
>> - const __be32 *prop;
>> - int len;
>> - phys_addr_t cap_mem_addr;
>> - phys_addr_t cap_mem_size;
>> + struct memblock_region rgn[MAX_USABLE_RANGES] = {0};
>> + const __be32 *prop, *endp;
>> + int len, i = 0;
>>
>> if ((long)node < 0)
>> return;
>> @@ -985,16 +993,24 @@ static void __init early_init_dt_check_for_usable_mem_range(unsigned long node)
>> pr_debug("Looking for usable-memory-range property... ");
>>
>> prop = of_get_flat_dt_prop(node, "linux,usable-memory-range", &len);
>> - if (!prop || (len < (dt_root_addr_cells + dt_root_size_cells)))
>> + if (!prop)
>
> if (!prop || (len % (dt_root_addr_cells + dt_root_size_cells)))
OK.
>
>> return;
>>
>> - cap_mem_addr = dt_mem_next_cell(dt_root_addr_cells, &prop);
>> - cap_mem_size = dt_mem_next_cell(dt_root_size_cells, &prop);
>> + endp = prop + (len / sizeof(__be32));
>> + while ((endp - prop) >= (dt_root_addr_cells + dt_root_size_cells)) {
>
> for (i = 0; i < MAX_USABLE_RANGES, prop < endp; i++) {
>
>> + rgn[i].base = dt_mem_next_cell(dt_root_addr_cells, &prop);
>> + rgn[i].size = dt_mem_next_cell(dt_root_size_cells, &prop);
>> +
>> + pr_debug("cap_mem_regions[%d]: base=%pa, size=%pa\n",
>> + i, &rgn[i].base, &rgn[i].size);
>>
>> - pr_debug("cap_mem_start=%pa cap_mem_size=%pa\n", &cap_mem_addr,
>> - &cap_mem_size);
>> + if (++i >= MAX_USABLE_RANGES)
>> + break;
>
> And drop this if.
OK.
>
>> + }
>>
>> - memblock_cap_memory_range(cap_mem_addr, cap_mem_size);
>> + memblock_cap_memory_range(rgn[0].base, rgn[0].size);
>> + for (i = 1; i < MAX_USABLE_RANGES && rgn[i].size; i++)
>
> s/ &&/,/
Hi Rob:
The comma operator may not be suitable for logical judgment. The logical judgment
before commas (,) is ignored.
Here's my test：
C code：
int main()
{
int i, j;
printf("&&:\n");
for (i = 0, j = 0; i < 2 && j < 3; i++, j++)
printf("i=%d, j=%d\n", i, j);
printf("\ncomma:\n");
for (i = 0, j = 0; i < 2, j < 3; i++, j++) //(i < 2） before comma is ignored
printf("i=%d, j=%d\n", i, j);
return 0;
}
Output：
&&:
i=0, j=0
i=1, j=1
comma:
i=0, j=0
i=1, j=1
i=2, j=2
>
>> + memblock_add(rgn[i].base, rgn[i].size);
>> }
>>
>> #ifdef CONFIG_SERIAL_EARLYCON
>> --
>> 2.25.1
>>
>>
>
> .
>
