RE: [Xen-ia64-devel] PATCH: rewrite vcpu_get_psr

["Xu, Anthony" <anthony.xu@xxxxxxxxx>]

>>I have to re-read Dan's paper and linux code, but in PV mode we only correctly
>>support IT=DT=RT.
>>
>>(the same should be true for VTi BTW and incidently we can
>>easily write OS which cannot be virtualized by VTi!)

You are right in some degree.
As I mentioned
>
>Vpsr.it=rt=0, vpsr.dt=1, this happens at the very beginning of windows boot.


At this moment, code is running in region 0, data is also in region 0 and we 
use 
region 0 to emulate guest physical mode
VMM can't handle this situation if window doesn't use identical-identity 
mapping 
for DTLB. (identical-identity mapping refers to, for example 0x10000 is mapped 
to 0x10000)


Thanks,
Anthony



>From: xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx
>[mailto:xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Xu, Anthony
>Sent: 2007å5æ11æ 17:27
>To: tgingold@xxxxxxx
>Cc: Xen-ia64-devel
>Subject: RE: [Xen-ia64-devel] PATCH: rewrite vcpu_get_psr
>
>>From: tgingold@xxxxxxx [mailto:tgingold@xxxxxxx]
>>Sent: 2007å5æ11æ 16:18
>>To: Xu, Anthony
>>Cc: Xen-ia64-devel
>>Subject: RE: [Xen-ia64-devel] PATCH: rewrite vcpu_get_psr
>>
>>Quoting "Xu, Anthony" <anthony.xu@xxxxxxxxx>:
>>
>>> >Tristan Gingold
>>> >Sent: 2007ÃÃ5ÃÃ11ÃÃ 13:23
>>> >To: Alex Williamson
>>> >Cc: Xen-ia64-devel
>>> >Subject: Re: [Xen-ia64-devel] PATCH: rewrite vcpu_get_psr
>>> >
>>> >> Unfortunately...
>>> >It's a little bit puzzling.  I didn't think the performace of mov =psr.l
>was
>>> >to important!
>>>
>>>
>>>
>>> +
>>> +   if (!PSCB(vcpu, metaphysical_mode))
>>> +           newpsr.i64 |= IA64_PSR_DT | IA64_PSR_RT | IA64_PSR_IT;
>>>
>>> -   if (PSCB(vcpu, metaphysical_mode))
>>> -           newpsr.dt = 0;
>>>
>>> Above old code would be translated to
>>>     if (PSCB(vcpu, metaphysical_mode))
>>>             newpsr.i64 &= ~IA64_PSR_DT;
>>I seriously think the old code was wrong (more precisely incorrect).
>>
>>I have to re-read Dan's paper and linux code, but in PV mode we only correctly
>>support IT=DT=RT.
>>
>>(the same should be true for VTi BTW and incidently we can
>>easily write OS which cannot be virtualized by VTi!)
>
>Machine psr dt it rt are always 1.
>While this code segment is used to emulate guest execution of "mov from psr"
>From the view of guest OS, vpsr dt it rt can be any value.
>
>In xenodomaim,
>There are only two situations.
>Virtual mode;  vpsr.it=dt=rt=1.
>Physical mode: vpsr.dt=0, vpsr.it=vpsr.rt=1, which happens in linux OS tlb 
>fault
>related handlers.
>
>In vti-domain.
>We support more situations except for above two.
>
>Vpsr.it=dt=rt=0, this happens when guest calls PAL call, which can be called
>only
>in physical mode.
>
>Vpsr.it=rt=0, vpsr.dt=1, this happens at the very beginning of windows boot.
>
>
>
>-Anthony
>
>

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