Re: [Xen-devel] [v3][PATCH 1/1] xen:vtd: missing RMRR mapping while share EPT

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

On 2014/7/24 19:11, Tim Deegan wrote:
> At 19:00 +0800 on 24 Jul (1406224818), Tiejun Chen wrote:
> > intel_iommu_map_page() does nothing if VT-d shares EPT page table.
> > So rmrr_identity_mapping() never create RMRR mapping but in some
> > cases like some GFX drivers it still need to access RMRR.
> >
> > Here we will create those RMRR mappings even in shared EPT case.
> >
> > Signed-off-by: Tiejun Chen <tiejun.chen@xxxxxxxxx>
> For the interaction with p2m code:
>
> Acked-by: Tim Deegn <tim@xxxxxxx>
Thanks a lot.

> though I am still worried about what happens if this overwrites an
> existing mapping.
As I understand RMRR should be specific. Its unlikely created for 
different mapping since this should be fixed in BIOS phase. And this is 
why that function is named as rmrr_identity_mapping().
Tiejun

> Tim.
>
> > ---
> >   xen/drivers/passthrough/vtd/iommu.c | 10 ++++++++--
> >   1 file changed, 8 insertions(+), 2 deletions(-)
> >
> > v3:
> >
> > * Use set_mmio_p2m_entry() to replace p2m_set_entry()
> > * Use ASSERT to check
> >
> > v2:
> >
> > * Fix coding style.
> > * Still need to abide intel_iommu_map_page(), so we should do nothing
> >    if dom0 and iommu supports pass thru.
> >
> > diff --git a/xen/drivers/passthrough/vtd/iommu.c 
> > b/xen/drivers/passthrough/vtd/iommu.c
> > index 042b882..f08a1fc 100644
> > --- a/xen/drivers/passthrough/vtd/iommu.c
> > +++ b/xen/drivers/passthrough/vtd/iommu.c
> > @@ -1867,8 +1867,14 @@ static int rmrr_identity_mapping(struct domain *d,
> >
> >       while ( base_pfn < end_pfn )
> >       {
> > -        if ( intel_iommu_map_page(d, base_pfn, base_pfn,
> > -                                  IOMMUF_readable|IOMMUF_writable) )
> > +        if ( iommu_use_hap_pt(d) )
> > +        {
> > +            ASSERT(!iommu_passthrough || !is_hardware_domain(d));
> > +            if ( set_mmio_p2m_entry(d, base_pfn, _mfn(base_pfn)) )
> > +                return -1;
> > +        }
> > +        else if ( intel_iommu_map_page(d, base_pfn, base_pfn,
> > +                                       IOMMUF_readable|IOMMUF_writable) )
> >               return -1;
> >           base_pfn++;
> >       }
> > --
> > 1.9.1
> >
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxx
> > http://lists.xen.org/xen-devel
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