On 07/20/2015 03:06 PM, Chen, Tiejun wrote:
>>>> +/* Find the lowest RMRR higher than base. */
>>>> +static int find_next_rmrr(uint32_t base)
>>>> +{
>>>> + unsigned int i;
>>>> + int next_rmrr = -1;
>>>> + uint64_t min_base = (1ull << 32);
>>>> +
>>>> + for ( i = 0; i < memory_map.nr_map ; i++ )
>>>> + {
>>>> + if ( memory_map.map[i].type == E820_RESERVED &&
>>>> + memory_map.map[i].addr > base &&
>>>> + memory_map.map[i].addr < min_base )
>>>> + {
>>>> + next_rmrr = i;
>>>> + min_base = memory_map.map[i].addr;
>>>> + }
>>>> + }
>>>> + return next_rmrr;
>>>> +}
>>>
>>> Considering _both_ callers, I think the function should actually return
>>> the lowest RMRR higher than or equal to base.
>>
>> You mean instead of strictly greater than the base.
>>
>>> Or wait - we actually
>>> need to find the lowest RMRR the _end_ of which is higher than base.
>>
>> Yes, you're right: there's always a risk that pci_mem_start will *start*
>> in the middle of a range. Looking for the next *end* is more robust.
>>
>
> Sorry this is not very clear to me so are you saying something like this?
>
> for ( i = 0; i < memory_map.nr_map ; i++ )
> {
> end = memory_map.map[i].addr + memory_map.map[i].size;
>
> if ( memory_map.map[i].type == E820_RESERVED &&
> end > base &&
> memory_map.map[i].addr < min_base )
> {
> next_rmrr = i;
> min_base = memory_map.map[i].addr;
> }
> }
I think replace min_base with min_end:
if ( memory_map.map[i].type == E820_RESERVED &&
end > base &&
end < min_end )
{
next_rmrr = i;
min_end = end;
}
Hmm... although I suppose that doesn't catch the possibility of a memory
range crossing the 4G boundary.
-George
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