Re: [Qemu-devel] [PATCH v3 1/2] intel_iommu: check validity for GAW bits in CE

[Peter Xu <peterx@redhat.com>]

On Wed, Dec 14, 2016 at 04:48:42AM +0200, Michael S. Tsirkin wrote:
> On Wed, Dec 14, 2016 at 10:09:04AM +0800, Peter Xu wrote:
> > Currently vt-d Context Entry (CE) only allows 39/48 bits address width.
> > If guest software configured more than that, we complain and report.
> > 
> > Signed-off-by: Peter Xu <peterx@redhat.com>
> > ---
> >  hw/i386/intel_iommu.c          | 17 ++++++++++++++++-
> >  hw/i386/intel_iommu_internal.h |  2 ++
> >  2 files changed, 18 insertions(+), 1 deletion(-)
> > 
> > diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> > index 5f3e351..517a2a3 100644
> > --- a/hw/i386/intel_iommu.c
> > +++ b/hw/i386/intel_iommu.c
> > @@ -599,9 +599,19 @@ static inline uint32_t vtd_get_level_from_context_entry(VTDContextEntry *ce)
> >      return 2 + (ce->hi & VTD_CONTEXT_ENTRY_AW);
> >  }
> >  
> > +/* Return 0 if failed to fetch valid aw */
> >  static inline uint32_t vtd_get_agaw_from_context_entry(VTDContextEntry *ce)
> >  {
> > -    return 30 + (ce->hi & VTD_CONTEXT_ENTRY_AW) * 9;
> > +    uint8_t aw = (ce->hi & VTD_CONTEXT_ENTRY_AW);
> > +    /*
> > +     * According to vt-d spec 10.4.2 bits 12:8, SAGAW only allows
> > +     * 39/48 bits.
> > +     */
> > +    if (aw > VTD_CE_AW_48BIT) {
> 
> 5-level is almost sure to allow more. I don't see the point of this test.

Please check above comment - spec only allow 3/4 level page table.

My version of vt-d spec is 2016 Oct. I suppose that's new enough...

-- peterx