Re: [PATCH 03/11] Handle asynchronous page fault in a PV guest.

[Avi Kivity <avi@redhat.com>]

On 11/03/2009 04:32 PM, Marcelo Tosatti wrote:
> Any attempt to access the swapped out data will cause a #PF vmexit,
> since the translation is marked as not present. If there's swapin in
> progress, you wait for that swapin, otherwise start swapin and wait.
>
> Its not as efficient as paravirt because you have to wait for a timer
> interrupt and the guest scheduler to decide to taskswitch, but OTOH its
> transparent.
>    

With a dyntick guest the timer interrupt will come at the end of the 
time slice, likely after the page has been swapped in.  That leaves smp 
reschedule interrupts and non-dyntick guests.

An advantage is that there is one code path for apf and non-apf.  
Another is that interrupts are processed, improving timekeeping and 
maybe responsiveness.


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