Re: [PATCH 0/5] Threaded MSI interrupt for VFIO PCI device

Alex Williamson
2015-12-03T18:55:55Z

On Thu, 2015-12-03 at 10:22 -0800, Yunhong Jiang wrote:
> When assigning a VFIO device to a KVM guest with low latency requirement, it
> is better to handle the interrupt in the hard interrupt context, to reduce
> the context switch to/from the IRQ thread.
>
> Based on discussion on https://lkml.org/lkml/2015/10/26/764, the VFIO msi
> interrupt is changed to use request_threaded_irq(). The primary interrupt
> handler tries to set the guest interrupt atomically. If it fails to achieve
> it, a threaded interrupt handler will be invoked.
>
> The irq_bypass manager is extended for this purpose. The KVM eventfd will
> provide a irqbypass consumer to handle the interrupt at hard interrupt
> context. The producer will invoke the consumer's handler then.

Do you have any performance data? Thanks,

Alex