Re: [Qemu-devel] [RFC] create a single workqueue for each vm to update vm irq routing table

Paolo Bonzini
2013-11-28T09:53:55Z

Il 28/11/2013 10:49, Avi Kivity ha scritto:
> Linux is safe, it does interrupt migration from within the interrupt
> handler. If you do that before the device-specific EOI, you won't get
> another interrupt until programming the MSI is complete.
>
> Is virtio safe? IIRC it can post multiple interrupts without guest acks.
>
> Using call_rcu() is a better solution than srcu IMO. Less code changes,
> consistently faster.

call_rcu() has the problem of rate limiting, too. It wasn't such a
great idea, I think.

The QRCU I linked would work great latency-wise (it has roughly the same
latency of an rwsem but readers are lock-free). However, the locked
operations in the read path would hurt because of cache misses, so it's
not good either.

Paolo