Re: [PATCH] x86: fix ref-counting bug in change_page_attr()

From: Jan Beulich
Date: Fri Dec 14 2007 - 03:38:20 EST


>>> Jeremy Fitzhardinge <jeremy@xxxxxxxx> 14.12.07 08:12 >>>
>Jan Beulich wrote:
>> When either calling change_page_attr() with the default attributes
>> pages in the direct mapping have and a page's attributes already were
>> set to the default or when changing the attributes from one non-default
>> value to another, the reference counting broke, leading to either
>> premature restoration of a large page or missing the opportunity to do
>> so.
>>
>> At the same time, make __PHYSICAL_MASK_SHIFT on 64-bits the value it
>> architecturally ought to have.
>>
>
>Could you put this in a separate patch? I have a bunch of page*.h and
>pgtable*.h refactoring patches which will conflict with this.

I doesn't seem logical to do so: The patch needs to introduce the definitions
for 32-bits (in order to define pte_pgprot()), and not doing the adjustment
for 64-bits here means (a) becoming inconsistent and (b) the pte_pgprot()
there would be incorrect. So such a split out patch would need to be a pre-
requisite to the one here, which wouldn't help avoiding the collisions with
your unification patches.

Jan

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