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Re: [Xen-devel] Re: Linux Stubdom Problem

On Tue, 23 Aug 2011, Tim Deegan wrote:
> At 20:36 +0100 on 22 Aug (1314045383), Stefano Stabellini wrote:
> > The current implementation of IOCTL_PRIVCMD_MMAPBATCH is only capable of
> > mapping foreign mfns into the address space of the caller, while we need
> > to remap a set of pages already mapped in the address space of the
> > caller to some gmfns of a foreign domain. In other words we need the
> > same functionality but in the other direction.
> I think I was confused whan you told me about this yesterday.  Do you
> need to map some of the linux-qemu-dom's memory into the guest?
> In that case, I think you can just grant the pages to the guest VM and
> use XENMAPSPACE_grant_table to map them. 

Yes, the pages I need to map into the guest have been vmalloc'ed by
xen_fbfront and mmap'ed into Qemu.
I didn't realize we could use any gmfn we wanted with

Jiageng: in the Linux implementation of the new ioctl, you can just call
gnttab_grant_foreign_access to grant access to the guest to framebuffer,
then you can use HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp) with
XENMAPSPACE_grant_table and the returned grant reference as idx to map
the pages into the guest.

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