On Thu, Oct 10, 2013 at 02:14:16PM +0200, Gerd Hoffmann wrote:
Hi,
I think the simplest way to do all this is simply to tell seabios that we have more memory. seabios already programs 64 bit BARs higher than memory.
Hmm? As I understand Igor just wants some address space for memory hotplug. So there wouldn't be memory there (yet). And telling seabios there is although there isn't will make seabios place wrong info into the e820 tables. Not going to fly.
True. Maybe we should get some smbios stuff from qemu too.
I think the issue is with legacy guests. E.g. if VCPU claims to support 50 bit of memory do we put high PCI memory at 1 << 50? If yes old guests which expect at most 40 bit will not be able to use it.
Hmm. Sure such guests exist?
I wouldn't be surprised. At least some windows guests crash if you try to tell them your system has too much physical memory (e.g. 2^48).
Note this is physical address lines, not virtual address space (where you might need an additional level of pagetables to fully use it, which is not something we could expect old guests being able to handle).
cheers, Gerd