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Re: [Qemu-devel] [PATCH] RFC kvm irqfd: add directly mapped MSI IRQ supp

From: Benjamin Herrenschmidt
Subject: Re: [Qemu-devel] [PATCH] RFC kvm irqfd: add directly mapped MSI IRQ support
Date: Mon, 24 Jun 2013 07:36:25 +1000

On Sun, 2013-06-23 at 17:07 +0300, Michael S. Tsirkin wrote:
> Yes I think that's fine really.
> Basically devices all speak MSIMessage as they should -
> this is what the PCI spec says.        
> On all normal systems guests also speak MSIMessage so
> the API which uses these makes sense for kvm.
> Except, ppc architecture in its wisdom decided to hide this
> in firmware.  QEMU does not have firmware so the translation
> has to be maintained in QEMU powerpc code.

It is still not enough. There is nothing that says that an MSI
address/message is unique. On pseries (among others I'm sure), this is a
per-host-bridge concept since the MSIs are decoded by the PHB and turned
into standard fabric interrupts there.

So at least the bus needs to be passed as well.


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