Re: [Xen-devel] [PATCH v5 8/8] x86/iommu: add map-reserved dom0-iommu option to map reserved memory ranges

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

On Fri, Aug 17, 2018 at 05:08:08AM -0600, Jan Beulich wrote:
> >>> On 14.08.18 at 15:43, <roger.pau@xxxxxxxxxx> wrote:
> > @@ -185,7 +219,13 @@ void __hwdom_init arch_iommu_hwdom_init(struct domain 
> > *d)
> >          if ( !hwdom_iommu_map(d, pfn, max_pfn) )
> >              continue;
> >  
> > -        rc = iommu_map_page(d, pfn, pfn, IOMMUF_readable|IOMMUF_writable);
> > +        if ( iommu_use_hap_pt(d) )
> > +        {
> > +            ASSERT(is_hvm_domain(d));
> > +            rc = set_identity_p2m_entry(d, pfn, p2m_access_rw, 0);
> > +        }
> > +        else
> > +            rc = iommu_map_page(d, pfn, pfn, 
> > IOMMUF_readable|IOMMUF_writable);
> 
> Why iommu_use_hap_pt()? Shouldn't HAP with or without shared
> page tables as well as shadow all get the same in-sync p2m and
> IOMMU mappings?

iommu_map_page is a noop if iommu_use_hap_pt is true (see
intel_iommu_map_page for example). Hence in the case the IOMMU page
tables are shared with HAP the pages must be added to the p2m.

I could switch this to use set_identity_p2m_entry if the guest is
auto-translated and only use iommu_map_page for non-autotranslated
guests.

Thanks, Roger.

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