Re: [PATCH] KVM: Add KVM_CAP_IRQ_ARCH capability

[Paul Mackerras <paulus@samba.org>]

On Thu, Mar 14, 2013 at 08:03:30PM +0100, Alexander Graf wrote:
> 
> On 14.03.2013, at 19:35, Scott Wood wrote:
> 
> > On 03/14/2013 01:33:30 PM, Alexander Graf wrote:
> >> We also want int pic_fd, no?
> > 
> > Not sure we really need that on the vcpu.  We'll need it on the vm unless we add it as an arg to the vcpu cap enable.
> 
> I don't think we need anything vm global for the cpu <-> PIC connections. Also, if you want to deregister a CPU (hotplug remove), you probably want to tell the PIC that the CPU has gone.

I had kvm_arch_vcpu_free() calling a release function for the selected
PIC, which should be enough to let the PIC know the CPU has gone away,
I would think.

I agree we don't need anything vm global.  The only vm ioctl which
needs to care about interrupt controllers is KVM_IRQ_LINE, and the
approach I take in my patchset is just to call all of the compiled-in
interrupt controllers until one of them takes it.  That assumes that
each irq architecture adds its own private data pointer to kvm->arch
if it's compiled in, which is feasible provided there are only a few
architectures supported, and gives the advantages of strong typing.
I did it this way because with the irq architecture being specified
per vcpu, there is no overall vm global irq architecture.

Paul.