Re: [Xen-devel] [BUG 1747]Guest could't find bootable device with memory more than 3600M

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

On 12/06/13 15:19, Jan Beulich wrote:
> > > > On 12.06.13 at 16:02, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
> > Il 12/06/2013 09:49, Jan Beulich ha scritto:
> > > > #3 should be possible or even the default (would need to check), but #4
> > > > is probably a bit harder to do.  Perhaps you can use a magic I/O port
> > > > for the xen platform PV driver, but if you can simply use two PCI
> > > > windows it would be much simpler because that's the same that TCG and
> > > > KVM already do.  The code is all there for you to lift in SeaBIOS.
> > > What is the connection here to the platform PV driver?
> > It's just a hook you already have for Xen-specific stuff in QEMU.
> Oh, sorry, I'm generally taking this term to refer to a Linux
> component.
>
> > > > Only Windows XP and older had problems with that because they didn't
> > > > like something in the ASL; but the 64-bit window is placed at the end of
> > > > RAM, so in principle any PAE-enabled OS can use it.
> > > At the end of _RAM_???
> > Why the question marks? :)
> Ah, so mean right after RAM. "At the end of RAM" reads like
> overlapping (and discarding) the tail of it.
>
> > If you have 4GB of RAM it will end at 0x140000000 (or something like
> > that) and that's where the 64-bit window starts.  Of course if you have
> > no RAM above the PCI hole, the 64-bit window will start at 0x100000000.
> So there's no provision whatsoever for extending the amount of RAM
> a guest may see? This is why I'd see any such allocation strategy to
> start at the end of physical address space, moving downwards.
Is there a mechanism to do memory hot-plug in qemu at the moment? If 
not, then there's no reason to put it anywhere else.
 -George


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