Messages in this thread | | | Date | Wed, 15 Mar 2006 17:33:33 -0800 | From | Zachary Amsden <> | Subject | Re: VMI Interface Proposal Documentation for I386, Part 5 |
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Pavel Machek wrote: >> from the hypervisor perspective - if the guest enables interrupts, and >> you have something pending to deliver, for correctness, you have to >> deliver it, right now. But does the kernel truly require that interrupt >> deliver immediately - in most cases, no. In particular, on the fast >> > > I'd say PCI hardware can delay interrupts for any arbitrary > delay... so if driver expects to get them "immediately", I'd say it is > broken. It should be enough to deliver them "soon enough", like not > more than 1msec late... >
I agree. One case we hit that did cause us a bug was local APIC delivery of self-IPIs. I didn't dig too deep into why Linux was unhappy without immediate delivery (we deferred delivery here unnecessarily, but did not stop it). I believe this was in SMP specific code that was using self-IPIs to regenerate IRQs .
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