Re: [Xen-devel] [RFC v2]Proposal to allow setting up shared memory areas between VMs from xl config file

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Fri, 23 Jun 2017, Zhongze Liu wrote:
> Hi Julien,
> 
> 2017-06-21 1:29 GMT+08:00 Julien Grall <julien.grall@xxxxxxx>:
> > Hi,
> >
> > Thank you for the new proposal.
> >
> > On 06/20/2017 06:18 PM, Zhongze Liu wrote:
> >>
> >> In the example above. A memory area ID1 will be shared between vm1 and
> >> vm2.
> >> This area will be taken from vm1 and mapped into vm2's stage-2 page table.
> >> The parameter "prot=RO" means that this memory area are offered with
> >> read-only
> >> permission. vm1 can access this area using gmfn1~gmfn2, and vm2 using
> >> gmfn5~gmfn6.
> >
> >
> > [...]
> >
> >>
> >> ======================================
> >> 2.3 mapping the memory areas
> >> ======================================
> >> Handle the newly added config option in tools/{xl, libxl} and utilize
> >> toos/libxc to do the actual memory mapping. Specifically, we will use
> >> a wrapper to XENMME_add_to_physmap_batch with XENMAPSPACE_gmfn_foreign to
> >> do the actual mapping. But since there isn't such a wrapper in libxc,
> >> we'll
> >> have to add a new wrapper, xc_domain_add_to_physmap_batch in
> >> libxc/xc_domain.c
> >
> >
> > In the paragrah above, you suggest the user can select the permission on the
> > shared page. However, the hypercall XENMEM_add_to_physmap does not currently
> > take permission. So how do you plan to handle that?
> >
> 
> I think this could be done via XENMEM_access_op?

I discussed this topic with Zhongze. I suggested to leave permissions as
"TODO" for the moment, given that for the use-case we have in mind they
aren't needed.

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