On Fri, Jul 02, 2021 at 11:55:40AM -0400, Michael S. Tsirkin wrote:
> On Fri, Jul 02, 2021 at 11:05:54PM +0800, Ming Lei wrote:
> > blk-mq needs to know if the device uses managed irq, so add one field
> > to virtio_device for recording if device uses managed irq.
> >
> > If the driver use managed irq, this flag has to be set so it can be
> > passed to blk-mq.
> >
> > Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
> > Cc: Jason Wang <jasowang@xxxxxxxxxx>
> > Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
> > Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
>
>
> The API seems somewhat confusing. virtio does not request
> a managed irq as such, does it? I think it's a decision taken
> by the irq core.
vp_request_msix_vectors():
if (desc) {
flags |= PCI_IRQ_AFFINITY;
desc->pre_vectors++; /* virtio config vector */
vdev->use_managed_irq = true;
}
err = pci_alloc_irq_vectors_affinity(vp_dev->pci_dev, nvectors,
nvectors, flags, desc);
Managed irq is used once PCI_IRQ_AFFINITY is passed to
pci_alloc_irq_vectors_affinity().
>
> Any way to query the irq to find out if it's managed?
So far the managed info isn't exported via /proc/irq, but if one irq is
managed, its smp_affinity & smp_affinity_list attributes can't be
changed successfully.
If irq's debugfs is enabled, this info can be retrieved.
Thanks,
Ming
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