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SubjectRe: Populating multiple ptes at fault time
Avi Kivity wrote:
>> Do you need to set the A bit synchronously?
>
> Yes, of course (if no guest cooperation).

Is the A bit architecturally guaranteed to be synchronously set? Can
speculative accesses set it? SDM vol 3 is a bit vague about it.

> I'll fail my own unit tests.
>
> If we add an async mode for guests that can cope, maybe this is
> workable. I guess this is what you're suggesting.
>

Yes. At worst Linux would underestimate the process RSS a bit
(depending on how many unsynchronized ptes you leave lying around). I
bet there's an appropriate pvop hook you could use to force
synchronization just before the kernel actually inspects the bits
(leaving lazy mode sounds good).

J


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