On 29/04/14 16:25, Dario Faggioli wrote:
> On gio, 2014-04-24 at 22:06
+0100, Andrew Cooper wrote:
>> * Don't walk off the end of p2m_table under the mistaken
impression that it
>> contains toolstack unsigned longs. Despite its array
type it contains guest
>>ÂÂ unsigned longs so unconditionally needs casting to the
guest width to use
>> correctly. Furthermore, a 64bit toolstack must be
extra careful when it
>>ÂÂ finds a 32bit guest's INVALID_MFN.
>>
>> * Drop 'mapped' and 'pinned' descriptions. This are both
bogus, including all
>>ÂÂ uses of the is_mapped() macro.
>>
> Just a question, what do you mean by 'bogus' here? About
pinned, I think
> I see it, and I like the way you put it in the patch. About
'mapped' and
> is_mapped()? Do you mean to say it's not useful information
here?
>
> Again, just curious.
The top bit of the type has nothing to do with mappings, or
certainly nothing that I am aware of, having successfully rewritten
PV migration from scratch.
The guest can still have mappings to its pinned pagetables, which
would have the top bit of the type set.
In xc_domain_save.c, this macro is used 4 times. 3 are used on mfns
and 1 is used on a type (for a bit of debugging code which appears
dead anyway). I expect noone has every tried migrating a PV domain
whose pages are located in mfns with the 44th bit set.
So by bogus, I mean the macro itself, and all uses of it.
My best guess is that is some vestigial code left over from a
previous way of doing things, although I didn't encounter anything
related to this in code archaeology I performed when trying to work
out why the legacy migration did certain things the way they did.
~Andrew
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