WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

[Xen-devel] Re: HYBRID: gnttab_map() to map shared frames..

On Tue, 2011-10-18 at 20:17 +0100, Mukesh Rathor wrote:
> On Tue, 18 Oct 2011 09:13:02 +0100
> Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> ... 
> > Could GNTTABOP_setup_table return GFNs from the very top of the GFN
> > space? Perhaps even above what would be architecturally valid,
> > although perhaps that is incompatible with HAP. Anything above
> > max_pfn would seem to be valid for the hypervisor to place "magic"
> > mappings in?
> 
> Well, what's confusing me for this is that there are few max 
> pfn's inside the guest! The nr_pages being one for example, then 
> there's max_pfn in shared_info.arch. I'm not sure if these two are in 
> sync with max_pfn in mm/bootmem.c. Then, we would need to adjust EPT to add 
> these pfns there. So that may put a damper on this.

What about using PFNs from right at the top, i.e. right up near
0xffffffff? I don't think there's any particular reason these special
PFNs need to be contiguous with the "regular" ones. This would limit the
total amount of RAM you could give a hybrid guest, but not by much.

> > Another approach might be to take advantage of the fact that a modern
> > PV kernel will call XENMEM_memory_map to obtain an e820 describing its
> > pseudo-physical address space. You could arrange for there to be some
> > reserved space returned in that.
> 
> I saw e820 code last night, and wondered if this might be the best option.
> I am glad you mentioned it. I am not much familiar with e820 format, so 
> studying it right now.
> 
> thanks,
> Mukesh
> 



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel