Re: [Xen-devel] question about xl migrate

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

>>> 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.

Perhaps for HVM guests.  Definitely not for PV guests however.

>>> 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.

That is covered by the later check.  This code needs to work for PV
guests as well as HVM guests.  You absolutely can't go deleting this
clause, or you will break migration for PV guests.

~Andrew

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