Re: Re: Xen: Hybrid extension patchset for hypervisor

[Jeremy Fitzhardinge <jeremy@goop.org>]

On 09/17/09 02:16, Ian Campbell wrote:
> In practise, at least for the 2.6.18-xen tree (which is the only one
> where I expect it was ever completely implemented), it is only used to
> set the kernel CS and DS and to gate sysenter setup (for which I think
> we have a better mechanism today) but you are right that in principle it
> could be more far reaching than that.
>   

Yeah.  Looks like the only other thing it allows is that the guest can
set arbitrary gdt entries.

>> Making use of XENFEAT_auto_translated_physmap would avoid the need for
>> identity p2m/m2p tables, but I'm not sure whether it still works.  I got
>> close to completely removing all references to it at one point, but I
>> think ia64 uses it?
>>     
> I very much expect that it'll need fixing/(re)implementing on both the
> kernel and hypervisor side...
>   

Yeah, I think the Xen side is missing altogether on x86 now.  I don't
think its worth recovering it unless its the ABI for making HAP
available to guests.  If IA64 is using it, then I think big parts of the
kernel are probably in OK shape (drivers, etc).

    J