Re: [Xen-devel] MSI-X interrupts to guests

[Espen Skoglund <espen.skoglund@xxxxxxxxxxxxx>]

Do you also map the vector to domU before requesting it?  You should
be able to map it as a GSI.  You'll also need c/s 791 or newer for the
domU kernel.

        eSk

[Kieran Mansley]
> Some recent changes from Espen Skoglund
> http://markmail.org/thread/76szuiywgd5dn2x4 suggest that it should now
> be possible to map an MSI-X interrupt direct to a guest.  However, when
> trying to do this, I get errors, and before I delve too deep I wondered
> if there was something obvious I'm doing wrong.

> My approach is that dom0 does something like this:

>       struct physdev_map_pirq map_irq;

>       map_irq.domid = guest_domid;
>       map_irq.type = MAP_PIRQ_TYPE_MSI;
>       map_irq.index = -1;
>       map_irq.pirq = -1;
>       map_irq.bus = pci_dev->bus->number;
>       map_irq.devfn = pci_dev->devfn;
>       map_irq.entry_nr = msix_entry;
>       map_irq.table_base = msix_table;

>       rc = HYPERVISOR_physdev_op(PHYSDEVOP_map_pirq, &map_irq);

> This call succeeds.  dom0 then tells the guest the value of map_irq.pirq
> (which seems to have a sensible value given the other interrupts mapped
> to that domain) that it gets back from this hypercall, and the guest
> tries to call request_irq() using that value.  The call to request_irq()
> returns -38 (ENOSYS).

> Any ideas what the problem could be?  I'm happy to investigate.

> Kieran


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