Re: [Q] mfn_to_gmfn macro, log-dirty bitmap,

[Min Lee <min.lee@gatech.edu>]

Thanks! now it gives me good numbers. seems to be working.
I thought M2P table is somehow enabled/disabled by paging_mode_translate(_d)...
So, does it mean M2P is working always regardless of 
paging_mode_translate(_d) ?
Then what paging_mode_translate(_d) exactly indicates?
Thanks a lot!
Min

On 6/28/2010 10:32 AM, Tim Deegan wrote:
> Hi,
>
> At 14:40 +0100 on 28 Jun (1277736059), Min Lee wrote:
>> Hi, folks.
>> I'm running 32bit PV-domu on 64bit xen&dom0 and I'm using
>> XEN_DOMCTL_SHADOW_OP_PEEK to get log-dirty bitmap.
>> First, I'm assuming this bitmap is indexed by gmfn, right? because we're
>> passing p2m->size parameter to xen.
>
> The log-dirty bitmap is indexed by guest _PFN_, even for PV guests.
> (see the comment at about line 400 of asm-x86/mm.h for an explanation of
> the *fn terminology, and the confusion around "gmfn" in particular).
>
>> Second, I have mfn (not gmfn) which I want to translate to gmfn so that I
>> can correctly read corresponding bit in log-dirty bitmap. so I've tried
>> mfn_to_gmfn() macro below but it doesn't seem to work. (always mfn==gmfn)
>> Maybe because m2p table is not enabled?
>
> The mfn_to_gmfn macro translates to GFNs (for historical reasons, IIRC
> to do with earlier shadow pagetable implementations).  To inspect the
> logdirty bitmap you want to translate to PFNs, so you should call
> get_gpfn_from_mfn() directly.
>
> Cheers,
>
> Tim.
>
>> How can I properly do mfn_to_gmfn?
>>
>> #define mfn_to_gmfn(_d, mfn)                            \
>>       ( (paging_mode_translate(_d))                       \
>>         ? get_gpfn_from_mfn(mfn)                          \
>>         : (mfn) )
>>
>>
>> Thanks for any help.
>> Min
>>
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>