Re: [Xen-ia64-devel] Faulty protection key handling

[Jürgen Gro? <juergen.gross@xxxxxxxxxxxxxxxxxxx>]

Hi Anthony,

Xu, Anthony wrote:
>> By the way, are there any thoughts about adding emulation of protection keys
>> to the hypervisor? I know, whether the hypervisor nor dom0-linux are using
>> this but we need this stuff. I would try to write a proposal and add using
>> protection keys in the minios for tests. What do you think?
> 
> Hi Dietmar,
> Frankly, due to there are no OS using protection key, I didn't think about it.
> While from architecture view, HVM should support protection key.
> 
> Can you provide more information about why you need to use protection key?

While Dietmar is just busy preparing the patches, I'm answering for him :-)
We are porting a /390 operating system to ia64/xen. /390 architecture is
using a protection key scheme to support memory protection, so using PKRs
is the natural design decision to minimize OS impact.

> 
> There are at least following things we need to do to emulate protection key 
> IMO.
> 1. Support long format VHPT. 
>       protection key is only used by long format VHPT, so we need to support 
> long format VHPT, as I know we already have some logic handling long format 
> VHPT, 
> I think we did fully support long format VHPT now.

No, just the other way round. PKR support is necessary for support of
long VHPT. You can use PKRs without any VHPT support at all.

Juergen

-- 
Juergen Gross                             Principal Developer
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