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

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Message-ID: <1449168953.15753.216.camel@redhat.com>
Date:	Thu, 03 Dec 2015 11:55:53 -0700
From:	Alex Williamson <alex.williamson@...hat.com>
To:	Yunhong Jiang <yunhong.jiang@...ux.intel.com>
Cc:	pbonzini@...hat.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/5] Threaded MSI interrupt for VFIO PCI device

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

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