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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Fri, 21 Jun 2013 15:12:13 +1000
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Subject: Re: [Qemu-devel] [PATCH] RFC kvm irqfd: add directly mapped MSI IRQ
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To: Alex Williamson <alex.williamson@redhat.com>
Cc: Anthony Liguori <aliguori@us.ibm.com>, "Michael S .
	Tsirkin" <mst@redhat.com>, Alexey Kardashevskiy <aik@ozlabs.ru>, qemu-devel@nongnu.org, Alexander Graf <agraf@suse.de>, qemu-trivial@nongnu.org, qemu-ppc@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>, Paul Mackerras <paulus@samba.org>, David Gibson <david@gibson.dropbear.id.au>

On Thu, 2013-06-20 at 22:46 -0600, Alex Williamson wrote:
> Maybe you could add a device parameter to kvm_irqchip_add_msi_route so
> that it can be implemented on POWER without this pci_bus_map_msi
> interface that seems very unique to POWER.  Thanks,

You mean unique to all non-x86 ? :-)

I believe almost everybody eventually turn MSIs into "normal"
interrupts...

Most often than not, the logic to do so is in the PCI Host Bridge.

The whole concept of passing the message address/data accross the
user/kernel interface is an x86 crackpotery but as is the entire
remapping/routing layer so ... :-)

Ben.