On 22.01.21 11:42, David Hildenbrand wrote:
> On 22.01.21 11:41, Anshuman Khandual wrote:
>>
>> On 1/22/21 2:48 PM, David Hildenbrand wrote:
>>>
>>>> +/*
>>>> + * Platforms should define arch_get_mappable_range() that provides
>>>> + * maximum possible addressable physical memory range for which the
>>>> + * linear mapping could be created. The platform returned address
>>>> + * range must adhere to these following semantics.
>>>> + *
>>>> + * - range.start <= range.end
>>>> + * - Range includes both end points [range.start..range.end]
>>>> + *
>>>> + * There is also a fallback definition provided here, allowing the
>>>> + * entire possible physical address range in case any platform does
>>>> + * not define arch_get_mappable_range().
>>>> + */
>>>> +struct range __weak arch_get_mappable_range(void)
>>>> +{
>>>> + struct range memhp_range = {
>>>> + .start = 0UL,
>>>> + .end = -1ULL,
>>>> + };
>>>> + return memhp_range;
>>>> +}
>>>> +
>>>> +struct range memhp_get_pluggable_range(bool need_mapping)
>>>> +{
>>>> + const u64 max_phys = (1ULL << (MAX_PHYSMEM_BITS + 1)) - 1;
>>>
>>> Sorry, thought about that line a bit more, and I think this is just
>>> wrong (took me longer to realize as it should). The old code used this
>>> calculation to print the limit only (in a wrong way), let's recap:
>>>
>>> Assume MAX_PHYSMEM_BITS=32
>>>
>>> max_phys = (1ULL << (32 + 1)) - 1 = 0x1ffffffffull;
>>>
>>> Ehm, these are 33 bit.
>>>
>>> OTOH, old code checked for
>>>
>>> if (max_addr >> MAX_PHYSMEM_BITS) {
>>>
>>> Which makes sense, because
>>>
>>> 0x1ffffffffull >> 32 = 1
>>>
>>> results in "true", meaning it's to big, while
>>>
>>> 0xffffffffull >> 32 = 0
>>>
>>> correctly results in "false", meaning the address is fine.
>>>
>>>
>>>
>>> So, this should just be
>>>
>>> const u64 max_phys = 1ULL << MAX_PHYSMEM_BITS;
>>>
>>> (similarly as calculated in virito-mem code, or in kernel/resource.c)
>>
>> Should this be 1ULL << MAX_PHYSMEM_BITS - 1 instead ? Currently there are
>
> Yes, obviously, sorry, forgot the -1.
>
const u64 max_phys = (1ULL << MAX_PHYSMEM_BITS) - 1;
to be precise.
--
Thanks,
David / dhildenb
