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From: Anthony Liguori <anthony@codemonkey.ws>
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Date: Mon, 24 Jun 2013 07:24:03 -0500
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Subject: Re: [Qemu-devel] [Qemu-ppc] [PATCH] RFC kvm irqfd: add directly
	mapped MSI IRQ support
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To: Alex Williamson <alex.williamson@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>, qemu-trivial@nongnu.org, qemu-devel <qemu-devel@nongnu.org>, qemu-ppc@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>, Paul Mackerras <paulus@samba.org>, David Gibson <david@gibson.dropbear.id.au>

Alex Williamson <alex.williamson@redhat.com> writes:

> On Sun, 2013-06-23 at 16:58 -0500, Anthony Liguori wrote:
>> Yeah, but none of this is Power specific...  so we can do the same for x86, no?
>> 
>> I'm still trying to wrap my head around why we need MSI knowledge at
>> all in the kernel for x86.  I presume it's to fast-path irqfd when
>> doing vhost?
>
> Or device assignment.  Any paths where we want to inject an MSI
> interrupt without going through userspace.  Thanks,

With VFIO, we use irqfd, if we program the irqfd as the underlying IRQ
that MSI would route to, isn't that sufficient?

That's more or less what Ben is proposing for Power...

Regards,

Anthony Liguori

>
> Alex