Increasing guest memory in Vancouver

Norman Feske norman.feske at ...1...
Fri Jul 20 18:03:58 CEST 2012

Hi Udo,

> Just to clarify this point:
> The hypervisor neither forces you to put Vancouver and its
> associated VM in the same PD, nor does it force you to have one
> instance of Vancouver per VM. You can create a PD, remotely create
> a vCPU in it and establish the VMX/SVM portals to point to some
> other PD. Then that other PD can manage its virtual address space
> any way it wants.

thanks. Let's keep that for the records. ;-)

> That said, we have found that putting both VMM and VM in the same
> PD has a number of advantages. First, a VMM needs to frequently
> access the memory of its VM, e.g., to look at the guest page
> tables. Having a 1:1 relationship between virtual memory in the VMM
> and guest-physical memory of the VM greatly simplifies that task.
> Second, if the VMM and VM were in different PDs, you'd pay for two
> additional address-space switches on each VM exit.

These are damn good arguments for the current design - I don't dare to
question them. So the 1:1 relationship between guest memory and
Vancouver's address space is actually not "imposed" by the kernel but
seems to be the most sensible design. Sorry that I mixed that up.


Dr.-Ing. Norman Feske
Genode Labs ·

Genode Labs GmbH · Amtsgericht Dresden · HRB 28424 · Sitz Dresden
Geschäftsführer: Dr.-Ing. Norman Feske, Christian Helmuth

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