>From: Jürgen Gro? [mailto:juergen.gross@xxxxxxxxxxxxxxxxxxx]
>Sent: 2007年4月26日 14:40
>To: Xu, Anthony
>Cc: Dietmar Hahn; xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
>Subject: Re: [Xen-ia64-devel] Faulty protection key handling
>
>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.
Yes, you are right.
But for short format VHPT, it is not easy to use PK, due to the protection key
is equal to rid by default. It is not flexible.
Usually protection key is related with long format VHPT,
I remember matt have made a long format VHPT patch for linux.( it is not in the
main tree), in this patch, protection key is used to implement TLB entry
sharing.
Anthony
>
>Juergen
>
>--
>Juergen Gross Principal Developer
>IP SW OS6 Telephone: +49 (0) 89 636 47950
>Fujitsu Siemens Computers e-mail: juergen.gross@xxxxxxxxxxxxxxxxxxx
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