Re: race with page_referenced_one->ptep_test_and_clear_young and pagetable setup/pulldown

[Jeremy Fitzhardinge <jeremy@goop.org>]

Keir Fraser wrote:
> I didn't think that nobbling config options for particular pv_ops
> implementations was acceptable? I'm rather out of the loop though, and could
> be wrong.
>   

As a workaround it would be OK.  As a dependency, perhaps.

> The PREEMPT_BITS limitation is a good argument for at least taking the pte
> locks in small batches though (small batches is preferable to one-by-one
> since we will want to batch the make-readonly-and-pin hypercall requests to
> amortise the cost of the hypervisor trap).
>   

Hm, that's a good point.  The pagetable permissions changes are batched
more or less asynchronously from the actual loop structure; that will
complicate adding the locking.

       J
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