Re: [Xen-devel] [RFC][PATCH 3/5] tools:libxc: remove mmio BAR out of RMRR mappings

["Chen, Tiejun" <tiejun.chen@xxxxxxxxx>]

On 2014/8/8 23:49, Jan Beulich wrote:
> > > > On 07.08.14 at 13:02, <tiejun.chen@xxxxxxxxx> wrote:
> > @@ -300,6 +302,30 @@ static int setup_guest(xc_interface *xch,
> >           goto error_out;
> >       }
> >
> > +    /* We need to move mmio range out of RMRR mapping. */
> > +    rc = xc_get_rmrr_map(xch, map, E820MAX);
> > +    if (rc < 0)
> > +    {
> > +        PERROR("Could not get RMRR info on domain");
> > +    }
> > +    else if ( rc )
> > +    {
> > +        for ( i = 0; i < rc; i++ )
> > +        {
> > +            rmrr_end = map[i].addr + map[i].size + 1;
> > +            if ( rmrr_end > mmio_start )
> > +            {
> > +                mmio_start = rmrr_end;
> > +            }
> > +        }
> This seems way too simplistic - what if the RMRRs are referring to
> memory regions extremely far apart?
>
> > +        mmio_size = (1ull << 32) - mmio_start;
> Limiting things to 4Gb?
>
> > +        if ( mmio_size <= 0 )
> mmio_size is an unsigned quantity, so this won't do what you intend.
Yes, you're right.

With a further consideration, mmio size should be configured so I think 
it may be enough just to check if current mmio is overlapping, then let 
user determine what next should do.
Please comments this in next revision directly.

Thanks
Tiejun
> Jan
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