RE: [v3 13/26] KVM: Define a new interface kvm_find_dest_vcpu() for VT-d PI

[Wu, Feng]

> -----Original Message-----
> From: Paolo Bonzini [mailto:paolo.bonzini@xxxxxxxxx] On Behalf Of Paolo
> Bonzini
> Sent: Saturday, December 20, 2014 9:17 PM
> To: Wu, Feng; Paolo Bonzini; Zhang, Yang Z; Thomas Gleixner; Ingo Molnar; H.
> Peter Anvin; x86@xxxxxxxxxx; Gleb Natapov; dwmw2@xxxxxxxxxxxxx;
> joro@xxxxxxxxxx; Alex Williamson; Jiang Liu
> Cc: iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; KVM list;
> Eric Auger
> Subject: Re: [v3 13/26] KVM: Define a new interface kvm_find_dest_vcpu() for
> VT-d PI
> 
> 
> 
> On 20/12/2014 00:48, Wu, Feng wrote:
> > In my understanding, lowest priority interrupts are always delivered to a
> > Single CPU, we need to find the right destination CPU from the cpumask.
> 
> Yes, but which CPU however differs every time the interrupt is
> delivered.  So the emulation here is a bit poor.  For now, please limit
> PI to fixed interrupts.

Do you mean we don't support Lowest priority interrupts? As I mentioned before,
Lowest priority interrupts is widely used in Linux, so I think supporting lowest priority
interrupts is very important for Linux guest OS. Do you have any ideas/suggestions about
how to support Lowest priority interrupts for PI? Thanks a lot!

Thanks,
Feng

> 
> > Actually, we don't support posting broadcast/multicast interrupts, because
> > the interrupt is associated with one Posted-interrupts descriptor, then one
> > vCPU.
> 
> Understood.
> 
> Paolo
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