Re: [PATCH v5 04/12] Provide special async page fault handler whenasync PF capability is detected

[Rik van Riel]

On 08/23/2010 11:48 AM, Avi Kivity wrote:

> Do you need to match cpu here as well? Or is token globally unique?
>
> Perhaps we should make it locally unique to remove a requirement from
> the host to synchronize? I haven't seen how you generate it yet.

If a task goes to sleep on one VCPU, but that VCPU ends
up not being runnable later on, it would be nice to wake
the task up on on a different VCPU.

I do not remember why it is safe to send this wakeup
event as an exception rather than an interrupt...

> The other cpu might be waiting for us to yield. We can fix it later with
> the the pv spinlock infrastructure.
>
> Or, we can avoid the allocation. If at most one apf can be pending (is
> this true?), we can use a per-cpu variable for this dummy entry.

Having a limit of just one APF pending kind of defeats
the point.

At that point, a second one of these faults would put
the VCPU to sleep, which prevents the first task from
running once its pagefault (which started earlier)
completes...

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