On Tue, Oct 08, 2013 at 11:33:31AM +0530, Bharat Bhushan wrote:
> We need to search linux "pte" to get "pte" attributes for
> setting TLB in KVM.
> This patch defines a linux_pte_lookup() function for same.
>
[snip]
> + /* wait until _PAGE_BUSY is clear */
> + while (1) {
> + pte = pte_val(*ptep);
> + if (unlikely(pte & _PAGE_BUSY)) {
> + cpu_relax();
> + continue;
> + }
> + }
> +
> + /* If pte is not present return None */
> + if (unlikely(!(pte & _PAGE_PRESENT)))
> + return __pte(0);
First, this looks racy to me, since nothing stops the compiler
refetching pte from memory, and it might have become busy again in the
meantime.
However, I don't think you need to do any of this, since the caller in
your next patch checks for pte_present(pte) anyway. On book E systems
we don't use _PAGE_BUSY, so you don't need the loop for your intended
application. I suggest you remove the entire section quoted above.
Paul.
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