[Xen-ia64-devel] RE: vcpu context merge

["Dong, Eddie" <eddie.dong@xxxxxxxxx>]

Magenheimer, Dan (HP Labs Fort Collins) wrote:
>> Magenheimer, Dan (HP Labs Fort Collins) wrote:
>>> 1) Can the shared page be mapped at a fixed or guest-requested
>>>    virtual address for non-VTI guests?   Xen needs to guarantee
>> Yes, I think they are mapped by guest TR. Actually this merge doesn't
>> change the way PV guest map the shared page. Maybe the only
>> difference is that this merge may introduce additional map for per
>> VP VPD. 
> 
> Just to make sure I understand:  I would like a PV guest to make
> a hypercall to Xen early on (probably in head.S prior to interrupts
> being enabled) that says:
> 
> Map the shared page at THIS virtual address.  (If an illegal virtual
> address is passed, Xen can kill the domain.)
So you mean you are using hypercall to do this kind of special map
instead of TR map, right?
Yes, this merge will not change this way, and if using hypercall to map
this virtual address is 
what you are prefered, that will be great as we are proposing a virtual
TR attribute in addtion 
to TC and TR for guest. So no change at this point or you will see a
extensive soliution for this.
> 
>> I know it introduce additional effort to do this in PV, kevin
>> and I can help together
>> to make that happen if you need :)
> 
> If all the virtual registers are a fixed offset from THIS
> virtual address (see xen-ia64.bkbits.net/xenlinux-ia64-2.6.11.bk
> in include/asm-ia64/xen/processsor.h), then only the
> offset constants need to change.  If you can provide me
> those constants for the new shared page, that would be
> very helpful.
Sure, I would like to suggest to generate this offset automatically like
asm-offsets.c
 did now for XEN, what is your opnion?
BTW, probably a single line change is needed to select the base address
of shared VPD instead of traditional shared page, as now XENO linux have
2 seperate shared pages, one for traditional shared page inf, and
another one for shared VPD.
> 
> Also, I noticed in some of the ctrl_if(?) code, some data
> structure is assumed to be at a fixed offset (1024) from
> the shared page.  Is this accounted for in your merged
> data structure?
I didn't understand well on this point, can u say more for ctrl_if?
How is it considered now? Will the merge change the way it works now?
Thanks,eddie

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