Re: [Qemu-devel] [RFC v1 2/3] intel_iommu: add 256 bits qi_desc support

[Tian, Kevin]

> From: Peter Xu [mailto:address@hidden
> Sent: Thursday, February 14, 2019 3:14 PM
> 
> >
> > > When 256 bits invalidation descriptor is used, the guest driver
> > > should be responsible to fill in zeros into reserved fields.
> > >
> > > Another question: is val[2] & val[3] used in any place even with
> > > 256bits mode?  From what I see from the spec (chap 6.5.2), all of them
> > > seems to be reserved as zeros, then I don't understand why bother
> > > extending this to 256bits...  Did I miss something?
> > >

PRQ is extended to carry larger private data which requires 256bits
mode. You can take a look at 7.5.1.1 Page Request Descriptor.

Thanks
Kevin