Re: [Xen-devel] [RFC][PATCH 02/13] introduce XENMEM_reserved_device_memory_map

[Tim Deegan <tim@xxxxxxx>]

At 16:10 +0100 on 16 Apr (1429200644), Jan Beulich wrote:
> >>> On 16.04.15 at 16:59, <tim@xxxxxxx> wrote:
> > At 17:21 +0800 on 10 Apr (1428686513), Tiejun Chen wrote:
> >> diff --git a/xen/include/public/memory.h b/xen/include/public/memory.h
> >> index 2b5206b..36e5f54 100644
> >> --- a/xen/include/public/memory.h
> >> +++ b/xen/include/public/memory.h
> >> @@ -574,7 +574,37 @@ struct xen_vnuma_topology_info {
> >>  typedef struct xen_vnuma_topology_info xen_vnuma_topology_info_t;
> >>  DEFINE_XEN_GUEST_HANDLE(xen_vnuma_topology_info_t);
> >>  
> >> -/* Next available subop number is 27 */
> >> +/*
> >> + * For legacy reasons, some devices must be configured with special memory
> >> + * regions to function correctly.  The guest would take these regions
> >> + * according to different user policies.
> >> + */
> > 
> > I don't understand what this means.  Can you try to write a comment
> > that would tell an OS developer:
> >  - what the reserved device memory map actually means; and
> >  - what this hypercall does.
> 
> For one, this is meant to be a tools only interface, hence the OS
> developer shouldn't care much. And then I don't think we should
> be explaining the RMRR concept here.

Fair enough.  How about:

/*
 * On some legacy devices, certain guest-physical addresses cannot
 * safely be used to map guest RAM.  This hypercall enumerates those
 * regions so the toolstack can avoid using them.
 */

Tim.

> >> @@ -121,6 +121,8 @@ void iommu_dt_domain_destroy(struct domain *d);
> >>  
> >>  struct page_info;
> >>  
> >> +typedef int iommu_grdm_t(xen_pfn_t start, xen_ulong_t nr, u32 id, void 
> >> *ctxt);
> > 
> > This needs a comment describing what the return values are.
> 
> Will do.
> 
> Jan
> 
> 
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