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xen-devel
Re: [Xen-devel] 32bit PAE PV guest on 64bit hypervisor
Keir Fraser wrote:
On 14/04/2009 04:39, "Mukesh Rathor" <mukesh.rathor@xxxxxxxxxx> wrote:
..
Implementing clear_fixmap() with set_pte() is not correct, even on native.
Since it clears high then low, it temporarily leaves you with a possibly
invalid present PTE -- even on native this can cause problems if e.g., the
invalid PTE maps uncacheable I/O memory.
In our kernel we simply solved this by implementing __set_fixmap() with a
hypercall that could update all 64 bits at once. An alternative is indeed to
clear low then high. Basically, clearing a pte has to be done the opposite
way round to setting a pte.
-- Keir
Just a quick update, I changed to hypercall and it worked. BTW, I also had to
increase the __PHYSICAL_MASK_SHIFT in guest (to 40) as I'm on system with
128GB. With both changes in the 32bit PAE guest, it's doing OK now.
Thanks for the help.
Mukesh
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