RE: [Xen-devel] Re: [Xen-users] rebased openSUSE Xen dom0 Patches

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> "Simon Graham" <simon.graham@xxxxxxxxxxxxxxxxxxx> 16.04.10 15:42 >>>
>We've actually narrowed the problem down a bit -- the pages we fail on
>are always in the range of those freed by free_init_pages("unused kernel
>memory") from free_initmem(). Now, the specific problem is that a
>writable page cant be turned into a page table page because it's page
>type ref count is non-zero -- I see in the free_init_pages() routine
>that two hypercalls are made for each page, one of which sets the pte to
>zero (which would decrement the page type ref count I think) and one of
>which does not -- doesn't this leave the page type ref count at 1 which
>in turn means the page cant be turned into a page table page? Or is
>there some other magic that occurs later on that should decrement the
>page type ref count before attempting to use the page as a page table
>page?

Are you observing this with both the .31 and .32 patches?

>Here's the extract of the code I am talking about (yes, we are using a
>64-bit Dom0):
>...

But that code is precisely what guarantees that the pages *can* be
converted to page table pages (by completely unmapping them from
the kernel image part of the address space). So your explanation is
rather confusing than clarifying to me...

Jan


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