On Wed, May 20, 2009 at 11:02:24PM +0300, Michael S. Tsirkin wrote:
> On Wed, May 20, 2009 at 09:38:58PM +0300, Blue Swirl wrote:
> > On 5/20/09, Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
> > > On Wed, May 20, 2009 at 08:44:31PM +0300, Blue Swirl wrote:
> > > > On 5/20/09, Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
> > > > > On Wed, May 20, 2009 at 08:21:01PM +0300, Blue Swirl wrote:
> > > > > > On 5/20/09, Michael S. Tsirkin <mst@xxxxxxxxxx> 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@xxxxxxxxxx>
> > > > > >
> > > > > > 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.
> > >
> > >
> > > Since "mondos" are not interrupts, why use irqs for them?
> >
> > I just said above that they are used for interrupt vector data. What
> > makes you think they are not interrupts?
>
> I'm sorry, I don't really know anything about sparc.
> All I am saying is that in PCI, interrupts never pass data,
> so qemu_set_irq as it is now, is a good API to send them.
>
> For the sparc feature you describe, you probably want to add
> a message data parameter to qemu_set_irq, but it's not
> really useful for MSI.
Just to clarify, the main difference is that with MSI/MSI-X
both data and address fields are mostly static, modifying them
involves ioapic and device updates which might be an expensive
operation (e.g. with kvm, needs an extra system call).
So I don't think it makes sense to pass MSI-X data field
with each call to qemu_set_irq.
--
MST
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