Hi Geert,
Am 30.01.2019 um 21:08 schrieb Geert Uytterhoeven:
The remainder is a fix for address wrap around when there is memory located
at the end of the 32-bit address space.
That part looks OK to me, and is still applicable.
I will retest with just the last part of the patch applied.
max_addr was reduced by one earlier in the last part, so isn't this one
min_low_pfn = availmem >> PAGE_SHIFT;
- max_low_pfn = max_addr >> PAGE_SHIFT;
+ max_low_pfn = (max_addr >> PAGE_SHIFT) + 1;
wrong? i.e. shouldn't we use
max_low_pfn = (max_addr+1) >> PAGE_SHIFT;
instead?
That would give 0 if max_addr = 0xffffffff, due to overflow.
Yep, figured that out right after hitting 'send'. The PFN doesn't
overflow, but wouldn't calculating end addresses from max_low_pfn lead
to overflow later on? It seems to me that max_low_pfn would point to the
page right after max_addr i.e. beyond end of memory? Is that expected
behaviour?
However, the workaround is not correct in the (unlikely) case where the
memory block size is not a multiple of PAGE_SIZE.
The only likely case would be the memory chunk containing the kernel,
i.e. availmem, and that's page aligned, so no problem there...
Cheers,
Michael
Gr{oetje,eeting}s,
Geert
