Re: [Xen-devel] [PATCH 2/2] x86: use pv-ops in {pte, pmd}_{set, clear}_flags()

[David Vrabel <david.vrabel@xxxxxxxxxx>]

On 21/03/14 18:18, David Vrabel wrote:
> Instead of using native functions to operate on the PTEs in
> pte_set_flags(), pte_clear_flags(), pmd_set_flags(), pmd_clear_flags()
> use the PV aware ones.

Looking at the history of this changes, these were introduced to avoid
PV ops for performance reasons.

I believe this can be fixed by making the numa-related PTE modifier
functions (pte_mknuma(), pte_mknonnuma()) use pte_modify() which is the
correct function to use when adjusting page protection.

I really do not understand how you're supposed to distinguish between a
PTE for a PROT_NONE page and one with _PAGE_NUMA -- they're identical.
i.e., pte_numa() will return true for a PROT_NONE protected page which
just seems wrong to me.

David

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