Hi Marc,
thanks for having a look!
On 29/03/17 09:30, Marc Zyngier wrote:
> On 02/02/17 16:32, Andre Przywara wrote:
>> If we need to inject an MSI into the guest, we rely at the moment on a
>> working GSI MSI routing functionality. However we can get away without
>> IRQ routing, if the host supports MSI injection via the KVM_SIGNAL_MSI
>> ioctl.
>> So we try the GSI routing first, but if that fails due to a missing
>> IRQ routing functionality, we fall back to KVM_SIGNAL_MSI (if that is
>> supported).
>>
>> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
>> ---
>> virtio/pci.c | 16 ++++++++++++++--
>> 1 file changed, 14 insertions(+), 2 deletions(-)
>>
>> diff --git a/virtio/pci.c b/virtio/pci.c
>> index 7cc0ba4..98bf6b7 100644
>> --- a/virtio/pci.c
>> +++ b/virtio/pci.c
>> @@ -193,8 +193,14 @@ static bool virtio_pci__specific_io_out(struct kvm *kvm, struct virtio_device *v
>>
>> gsi = irq__add_msix_route(kvm,
>> &vpci->msix_table[vec].msg);
>> - if (gsi >= 0)
>> + if (gsi >= 0) {
>> vpci->config_gsi = gsi;
>> + break;
>> + }
>> + if (gsi == -ENXIO &&
>> + vpci->features & VIRTIO_PCI_F_SIGNAL_MSI)
>> + break;
>> + die("failed to configure MSIs");
>> break;
>> case VIRTIO_MSI_QUEUE_VECTOR:
>> vec = ioport__read16(data);
>> @@ -205,8 +211,14 @@ static bool virtio_pci__specific_io_out(struct kvm *kvm, struct virtio_device *v
>>
>> gsi = irq__add_msix_route(kvm,
>> &vpci->msix_table[vec].msg);
>> - if (gsi < 0)
>> + if (gsi < 0) {
>> + if (gsi == -ENXIO &&
>> + vpci->features & VIRTIO_PCI_F_SIGNAL_MSI)
>> + break;
>> +
>> + die("failed to configure MSIs");
>> break;
>> + }
>> vpci->gsis[vpci->queue_selector] = gsi;
>
> Is it really expected to find -ENXIO in this array instead of a GSI?
Not sure I get this "in this array" comment here. Any negative return
value ends up in a break, without writing it anywhere.
Later on we check for VIRTIO_PCI_F_SIGNAL_MSI first before referencing
the array. This is admittedly a bit convoluted.
So shall I add comments here? Or rewrite the if statement to make this
more obvious?
Cheers,
Andre.
>
>> if (vdev->ops->notify_vq_gsi)
>> vdev->ops->notify_vq_gsi(kvm, vpci->dev,
>>
>
> Thanks,
>
> M.
>
