Messages in this thread | | | Date | Mon, 23 Aug 2010 11:52:23 -0400 | From | Rik van Riel <> | Subject | Re: [PATCH v5 04/12] Provide special async page fault handler when async PF capability is detected |
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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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