Re: [Xen-devel] address mapping between domains

[Mark Williamson <Mark.Williamson@xxxxxxxxxxxx>]

> > The domain that's controlling the real device (usually dom0) maps the
> > domU's memory before putting data into it (either directly or using PIO).
>
> Can I use this mechanism to make domU to share some pages in dom0? Where
> can I find the code, please?

Right now only privileged domains (i.e. dom0 or a driver domain) can map the 
memory of other domains.  Sharing will be more flexible once the grant tables 
work is done and the reverse operation will be possible.

Perhaps for your shared memory work you could initially test with sharing 
between dom0 and a single domU?  Then you can move to grant tables when 
they're ready to perform arbitrary sharing?

Cheers,
Mark

> > > Another question is about the hypercall: update_va_mapping. It has
> > > three arguments: vaddr, val, flags. Can anyone kindly explain the
> > > meaning of them and how they are used in the hypercall? Actually I am
> > > puzzled why there is no machine page id as an argument, since the
> > > virtual address should be mapped to a machine page anyway when the page
> > > table is updated.
> >
> > Arguments to this as as Chris described.
> >
> > Note that the backend drivers often use a "multicall" to perfrom multiple
> > operations (e.g. update multiple address mappings) in one hypercall.
>
> Yes, I have noticed it. Thanks a lot for help.
>
> --------------------------
> Zhiyi from EPFL Switzerland


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