Re: sparsemem & sparsemem extreme question

Heiko Carstens
2005-10-06T07:40:38Z

> > As already mentioned, we will have physical memory with the MSB set. Afaik
> > the hardware uses this bit to distinguish between different types of memory.
> > So we are going to have the full 64 bit address space.
> Is it just the MSB? If so, we can probably just shift it down to some
> reasonable address. The only issue comes if you really have the whole
> address space used in some random way.

Unfortunately there is more than just the MSB. If the MSB is set then there
will be a 'model dependent' number of bits just below the MSB used to encode
whatever the hardware thinks is necessary. Also you cannot tell how these
bits will be set from an operating system's view. Best thing to do is to
assume nothing and leave the addresses alone.

Heiko