Re: [Xen-devel] [PATCH v5 1/1] Add mmio_hole_size

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 09/30/2014 09:22 AM, George Dunlap wrote:
> On Tue, Sep 30, 2014 at 2:27 AM, Boris Ostrovsky
> <boris.ostrovsky@xxxxxxxxxx> wrote:
> > > +    if ( mmio_hole_size )
> > > +    {
> > > +        uint64_t max_ram_below_4g = (1ULL << 32) - mmio_hole_size;
> > > +
> > > +        if ( max_ram_below_4g > HVM_BELOW_4G_MMIO_START )
> > > +        {
> > > +            printf("max_ram_below_4g=0x"PRIllx
> > > +                   " too big for mmio_hole_size=0x"PRIllx
> > > +                   " has been ignored.\n",
> > > +                   PRIllx_arg(max_ram_below_4g),
> > > +                   PRIllx_arg(mmio_hole_size));
> > > +        }
> > Do you need to check whether the hole is too large?
> >
> > Here and in the toolstack.
> How large is too large?  I've seen real machines with a 3GiB memory hole...

But if mmio_hole_size is set to, say, 4GB we can't expect anything good, 
right? I don't know what the reasonable upper limit on it should be but 
it seems to me we need one. Especially given that it's a uint64_t.
-boris

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel