Re: [Xen-devel] question about xl migrate

["Zhang, Chunyu" <zhangcy@xxxxxxxxxxxxxx>]

hi Andrew
>On 17/05/16 10:01, Zhang, Chunyu wrote:
>> hi all
>>
>> i have two question about xl migrate
>>
>> write_batch
>> 120     for ( i = 0; i < nr_pfns; ++i )
>> 121     {
>> 122         types[i] = mfns[i] = ctx->save.ops.pfn_to_gfn(ctx,
>> 123                                                       
>> ctx->save.batch_pfns[i]);
>> 124 
>> 125         /* Likely a ballooned page. */
>> 126         if ( mfns[i] == INVALID_MFN )
>> 127         {
>> 128             set_bit(ctx->save.batch_pfns[i], ctx->save.deferred_pages);
>> 129             ++ctx->save.nr_deferred_pages;
>> 130         }
>> 131     }
>>
>> 1.  line 122
>> in hvm mode, is not mfns, but gfns.
>> right?
>
>Correct.  The array should be named "gfns" rather than "mfns", which is
>the appropriate term for both PV and HVM guests.
>
>>
>> 2. line 125
>> in hvm mode,would not be a balloon page.
>> gfn would not be INVALID_MFN.
>> mfn would be INVALID_MFN.
>> right?
>
>I don't understand what you asking here.

i think those code should delete:
>> 125         /* Likely a ballooned page. */
if page is ballooed, gfns is not  INVALID_MFN, but mormal.
>> 126         if ( mfns[i] == INVALID_MFN )
>> 127         {
>> 128             set_bit(ctx->save.batch_pfns[i], ctx->save.deferred_pages);
>> 129             ++ctx->save.nr_deferred_pages;
>> 130         }
those code is not for balloon.

when xc_get_pfn_type_batch is called,
ballooned page type is XEN_DOMCTL_PFINFO_XTAB
XEN_DOMCTL_PFINFO_XTAB is for ballooned pages.

>
>~Andrew
>
>

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