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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 04.11.16 at 18:25, <roger.pau@xxxxxxxxxx> wrote:
> 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.

True.

Jan


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