On 31.10.2024 14:19, oleksii.kuroc...@gmail.com wrote:
>>>>> +void __init setup_mm(void)
>>>>> +{
>>>>> + const struct membanks *banks = bootinfo_get_mem();
>>>>> + paddr_t ram_start = INVALID_PADDR;
>>>>> + paddr_t ram_end = 0;
>>>>> + paddr_t ram_size = 0;
>>>>> + unsigned int i;
>>>>> +
>>>>> + /*
>>>>> + * We need some memory to allocate the page-tables used
>>>>> for
>>>>> the directmap
>>>>> + * mappings. But some regions may contain memory already
>>>>> allocated
>>>>> + * for other uses (e.g. modules, reserved-memory...).
>>>>> + *
>>>>> + * For simplicity, add all the free regions in the boot
>>>>> allocator.
>>>>> + */
>>>>> + populate_boot_allocator();
>>>>> +
>>>>> + total_pages = 0;
>>>>> +
>>>>> + for ( i = 0; i < banks->nr_banks; i++ )
>>>>> + {
>>>>> + const struct membank *bank = &banks->bank[i];
>>>>> + paddr_t bank_end = bank->start + bank->size;
>>>>> +
>>>>> + ram_size += ROUNDDOWN(bank->size, PAGE_SIZE);
>>>>
>>>> As before - if a bank doesn't cover full pages, this may give the
>>>> impression
>>>> of there being more "total pages" than there are.
>>> Since it rounds down to PAGE_SIZE, if ram_start is 2K and the total
>>> size of a bank is 11K, ram_size will end up being 8K, so the "total
>>> pages" will cover less RAM than the actual size of the RAM bank.
>>
>> ram_start at 2k but bank size being 13k would yield 2 usable pages
>> (first partial page of 2k unusable and last partial page of 3k
>> unusable), yet ram_size of 12k (3 pages). You need to consider the
>> common case; checking things work for a randomly chosen example isn't
>> enough.
> Then I have to check separately the start and end of bank and check if
> ram_size should be reduced in case if the start or end isn't properly
> aligned.
All I think you need to do is align bank start up to a page boundary and
align bank end down to a page boundary.
Jan
