From mboxrd@z Thu Jan  1 00:00:00 1970
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [kvmarm] [RFC PATCH 0/3] KVM: ARM: Get rid of hardcoded VGIC
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Date: Sat, 27 Oct 2012 07:21:31 +1100
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Cc: Jan Kiszka <jan.kiszka@siemens.com>,
	Peter Maydell <peter.maydell@linaro.org>,
	Paul Mackerras <paulus@samba.org>,
	Christoffer Dall <c.dall@virtualopensystems.com>,
	Alexander Graf <agraf@suse.de>,
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	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	kvm-ppc <kvm-ppc@vger.kernel.org>
To: Paolo Bonzini <pbonzini@redhat.com>
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On Fri, 2012-10-26 at 13:57 +0200, Paolo Bonzini wrote:
> Il 26/10/2012 13:09, Benjamin Herrenschmidt ha scritto:
> > The only cases I can think of are the association between a virtual
> > interrupt (ie, an interrupt in the guest interrupt number space) and an
> > in-kernel source for that interrupt, ie, vhost and PCI pass-through
> > essentially.
> 
> If you exclude old-style PCI pass-through and limit yourself to vhost
> and VFIO, you can treat irqfd as "the" in-kernel source of the
> interrupt.  Then you need a mapping between MSIs and numbers used in
> KVM_IRQFD ("GSIs").

Argh. Ok, I get that we need a mapping between an irqfd and a global
number, I don't see where MSIs come into the picture at all here. At
least for us they don't.

> This is what KVM_SET_GSI_ROUTING modifies, and basically the mapping is
> modified every time a vector is masked/unmasked in the MSI-X table.

Right and that doesn't make sense for us. In fact I don't understand how
it makes sense for x86 either, but that's because I don't understand how
the APIC works I suppose.

Ben.