On Thu, 10 Oct 2013 15:21:32 +0300 "Michael S. Tsirkin" <[email protected]> wrote:
> 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). confirmed, the same happened when memory device was mapped too high, can't recall windows version tough. > > > 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 > > >
