I thought that one use case of VT-d2 interrupt remapping was to be able to 
safely and more efficiently deliver interrupts to the CPU that runs the 
particular VCPU of the guest that owns the I/O device that issues the 
interrupt. Shouldn't there at least be some performance (e.g. latency) 
improvement doing the remapping and checking in HW with a predefined table 
rather than multiplexing this in software in the hypervisor layer?

> -----Original Message-----
> From: Kay, Allen M [mailto:allen.m....@intel.com]
> Sent: 14 May 2009 15:02
> To: Fischer, Anna; kvm@vger.kernel.org
> Subject: RE: KVM & VT-d2?
> 
> We have verified VT-d2 features works with PCI passthrough on KVM.  To
> enable it, you need to turn on interrupt remapping in kernel config.
> 
> Interrupt remapping is a security/isolation feature where interrupt
> delivery is qualified with device's bus/device/function in interrupt
> remapping table entry when source ID checking is turn on.  It does not
> directly inject interrupt to the guest OS.
> 
> -----Original Message-----
> From: kvm-ow...@vger.kernel.org [mailto:kvm-ow...@vger.kernel.org] On
> Behalf Of Fischer, Anna
> Sent: Thursday, May 14, 2009 2:53 PM
> To: kvm@vger.kernel.org
> Subject: KVM & VT-d2?
> 
> Does KVM already take advantage of Intel VT-d2 features, e.g. interrupt
> remapping support? Has anyone verified how it improves interrupt
> delivery for PCI pass-through devices?
> 
> Thanks,
> Anna
> 
> 
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