Re: Populating multiple ptes at fault time

[Jeremy Fitzhardinge <jeremy@goop.org>]

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