Re: Questions about libdrm_intel and way to share physical memory between CPU and GPU

[Alan Cox <alan@lxorguk.ukuu.org.uk>]

> I'd much rather be able to just hand that memory off to the kernel to
> use along with everything else and have there be nothing magic about it.
> But as I recall, the mtrr mappings of that memory was often goofy, so it
> may take some work to clean it up.

That also depends where it is located - you'd need to add memory hot
plug, and in the general case (as opposed to the Intel i9xx case) that
memory may not be main memory anyway.

We can't go giving memory that is actually part of some other system
complex on some of the non Intel devices to the CPU for example. So yes
its a hack that works in limited cases for Intel to give the memory to
the system but you need 3 level page tables, memory hot plug and PAT
enabled to pull that off.

Either way the two appear to be different things, and both have their
uses.

Alan