Re: [Xen-devel] [PATCH v3.1 08/15] x86/vtd: fix mapping of RMRR regions

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

On Fri, Nov 04, 2016 at 11:08:21AM -0600, Jan Beulich wrote:
> >>> On 04.11.16 at 17:19, <roger.pau@xxxxxxxxxx> wrote:
> > On Fri, Nov 04, 2016 at 10:13:08AM -0600, Jan Beulich wrote:
> >> >>> On 04.11.16 at 16:33, <roger.pau@xxxxxxxxxx> wrote:
> >> > --- a/xen/include/asm-x86/p2m.h
> >> > +++ b/xen/include/asm-x86/p2m.h
> >> > @@ -834,6 +834,7 @@ static inline unsigned int 
> >> > p2m_get_iommu_flags(p2m_type_t p2mt)
> >> >      case p2m_grant_map_rw:
> >> >      case p2m_ram_logdirty:
> >> >      case p2m_map_foreign:
> >> > +    case p2m_mmio_direct:
> >> >          flags =  IOMMUF_readable | IOMMUF_writable;
> >> >          break;
> >> >      case p2m_ram_ro:
> >> 
> >> Generally this may be the route to go. But if we want to do so, we
> >> need to throughly understand why this type wasn't included here
> >> before (and I don't know myself).
> > 
> > It was me that introduced p2m_get_iommu_flags, and I just didn't think it 
> > would be useful at that point, that's why it wasn't included.
> 
> But there must have been logic to set the permissions before that?

Previous to that only p2m_ram_rw would get IOMMU mappings. I've tracked this 
back to ff635e12, but there's no mention there about why only p2m_ram_rw 
would get IOMMU mappings.

Considering that on hw with shared page-tables this is already available, I 
don't see an issue with also doing it for the non-shared pt case.

Roger.

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