Re: [Xen-devel] [BUG] After upgrade to Xen 4.12.0 iommu=no-igfx

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Mon, Jul 22, 2019 at 05:02:35PM +0200, Paul Durrant wrote:
> > -----Original Message-----
> > From: Roger Pau Monne <roger.pau@xxxxxxxxxx>
> > Sent: 22 July 2019 15:40
> > To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
> > Cc: 'Roman Shaposhnik' <roman@xxxxxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx; 
> > jgross@xxxxxxxx; Andrew
> > Cooper <Andrew.Cooper3@xxxxxxxxxx>; boris.ostrovsky@xxxxxxxxxx; 
> > jbeulich@xxxxxxxx
> > Subject: Re: [Xen-devel] [BUG] After upgrade to Xen 4.12.0 iommu=no-igfx
> > diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
> > index fef97c82f6..88a2430c8c 100644
> > --- a/xen/arch/x86/mm/p2m.c
> > +++ b/xen/arch/x86/mm/p2m.c
> > @@ -836,7 +836,7 @@ guest_physmap_add_page(struct domain *d, gfn_t gfn, 
> > mfn_t mfn,
> >           */
> >          for ( i = 0; i < (1UL << page_order); ++i, ++page )
> >          {
> > -            if ( !need_iommu_pt_sync(d) )
> > +            if ( !has_iommu_pt(d) )
> >                  /* nothing */;
> >              else if ( get_page_and_type(page, d, PGT_writable_page) )
> >                  put_page_and_type(page);
> > @@ -1341,7 +1341,7 @@ int set_identity_p2m_entry(struct domain *d, unsigned 
> > long gfn_l,
> > 
> >      if ( !paging_mode_translate(p2m->domain) )
> >      {
> > -        if ( !need_iommu_pt_sync(d) )
> > +        if ( !has_iommu_pt(d) )
> >              return 0;
> >          return iommu_legacy_map(d, _dfn(gfn_l), _mfn(gfn_l), PAGE_ORDER_4K,
> >                                  IOMMUF_readable | IOMMUF_writable);
> > @@ -1432,7 +1432,7 @@ int clear_identity_p2m_entry(struct domain *d, 
> > unsigned long gfn_l)
> > 
> >      if ( !paging_mode_translate(d) )
> >      {
> > -        if ( !need_iommu_pt_sync(d) )
> > +        if ( !has_iommu_pt(d) )
> >              return 0;
> >          return iommu_legacy_unmap(d, _dfn(gfn_l), PAGE_ORDER_4K);
> >      }
> 
> Yes, this all looks ok to me... although I still find it counterintuitive 
> that we make p2m calls for PV domains.

I agree, albeit I'm not sure of how to get rid of those, will need to
look at the callers. For iommu callers we could likely just call
iommu_legacy_{map/unmap} for PV.

I'm going to formally submit this patch then.

Thanks, Roger.

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