Re: [Xen-devel] [PATCH v5 06/10] IOMMU/MMU: propagate IOMMU Device-TLB flush error up to iommu_iotlb_flush{, _all} (top level ones).

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Tuesday, May 24, 2016 3:02 PM
> 
> >>> On 24.05.16 at 03:16, <quan.xu@xxxxxxxxx> wrote:
> > On May 24, 2016 12:06 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
> >> >>> On 18.05.16 at 10:08, <quan.xu@xxxxxxxxx> wrote:
> >> > --- a/xen/common/memory.c
> >> > +++ b/xen/common/memory.c
> >> > @@ -633,9 +633,9 @@ static long
> >> memory_exchange(XEN_GUEST_HANDLE_PARAM(xen_memory_exchange_t)
> >> arg)
> >> >      return rc;
> >> >  }
> >> >
> >> > -static int xenmem_add_to_physmap(struct domain *d,
> >> > -                                 struct xen_add_to_physmap *xatp,
> >> > -                                 unsigned int start)
> >> > +static int __must_check xenmem_add_to_physmap(struct domain *d,
> >> > +                                              struct xen_add_to_physmap
> > *xatp,
> >> > +                                              unsigned int start)
> >> >  {
> >>
> >> As before - either you do this adding of annotations completely, or you 
> >> stop
> > at
> >> the IOMMU / MM boundary.
> >
> > I prefer to stop at the IOMMU / MM boundary. The IOMMU boundary is obvious,
> > but what's the definition of MM boundary? I thought this is at MM boundary.
> 
> Not sure what you mean to understand. The IOMMU / MM boundary
> is the boundary between those two components, there's no talk of
> two boundaries here, and hence the question is unclear to me.
> 
> Jan

Hi, Quan,

A file-based map about IOMMU/MM boundary is under arch/x86/mm. You
need focus on low-level interaction between IOMMU and MM components,
i.e. when some state change in MM code (mostly p2m change) needs to 
conduct IOMMU operations.

Above xenmem is much higher level, which will be routed to various MM 
operations internally so you don't need bother here.

Thanks
Kevin

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