Re: [Xen-devel] [PATCH] tools/xl: disallow PCI device assignment for HVM guest when PoD is enabled

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2014-01-10 at 09:19 +0000, Jan Beulich wrote:
> >>> On 09.01.14 at 20:10, Wei Liu <wei.liu2@xxxxxxxxxx> wrote:
> > +    /* We cannot have PoD and PCI device assignment at the same
> > +     * time. VT-d engine needs to set up the entire page table for
> > +     * the domain. However if PoD is enabled, un-populated memory is
> > +     * marked as populate_on_demand, and VT-d engine won't set up page
> > +     * tables for them. Therefore any DMA towards those memory may
> > +     * cause DMA fault.
> > +     *
> > +     * This is restricted to HVM guest, as only VT-d is relevant
> > +     * in the counterpart in Xend. We're late in release cycle so the 
> > change
> > +     * should only does what's necessary. Probably we can revisit if
> > +     * we need to do the same thing for PV guest in the future.
> > +     */
> 
> The comment shouldn't say VT-d as long as the code isn't special
> casing VT-d.

Also this second paragraph looks more suitable to the commit message to
me.

Ian.


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