[SeaBIOS] [Qemu-devel] [RFC] map 64-bit PCI devices after all possible RAM
Michael S. Tsirkin
mst at redhat.com
Thu Oct 10 14:21:32 CEST 2013
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
>
More information about the SeaBIOS
mailing list