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Date: Wed, 20 May 2009 21:24:11 +0300
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api
Message-ID: <20090520175641.GB22935@redhat.com>
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To: Blue Swirl <blauwirbel@gmail.com>
Cc: Carsten Otte <cotte@de.ibm.com>, kvm@vger.kernel.org, Rusty Russell <rusty@rustcorp.com.au>, qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, Christian Borntraeger <borntraeger@de.ibm.com>, avi@redhat.com

On Wed, May 20, 2009 at 08:44:31PM +0300, Blue Swirl wrote:
> On 5/20/09, Michael S. Tsirkin <mst@redhat.com> wrote:
> > On Wed, May 20, 2009 at 08:21:01PM +0300, Blue Swirl wrote:
> >  > On 5/20/09, Michael S. Tsirkin <mst@redhat.com> wrote:
> >  > > define api for allocating/setting up msi-x irqs, and for updating them
> >  > >  with msi-x vector information, supply implementation in ioapic. Please
> >  > >  comment on this API: I intend to port my msi-x patch to work on top of
> >  > >  it.
> >  > >
> >  > >  Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> >  >
> >  > Sparc64 also uses packets ("mondos", not implemented yet) for
> >  > interrupt vector data, there the packet size is 8 * 64 bits.
> >  > I think we should aim for a more generic API that covers this case also.
> >
> >
> > Are you sure this is a good idea? MSI is tied to PCI, and PCI only has
> >  MSI, not "mondos". What code would benefit from this abstraction?
> 
> Sparc64 emulation, of course. I think also the API would be neater.
> 
> >  > For example, irq.c could support opaque packet payload of
> >  > unspecified/predefined size.  MSI packet structure should be defined
> >  > in ioapic.c.
> >
> >
> > Note that MSI does not have packets and MSI interrupts do not pass any payload.
> 
> I don't know too much about MSI, what's the 'data' field in msi_state then?

opaque stuff that apic uses to select irq and cpu.

-- 
MST