On Tue, Apr 7, 2015 at 6:54 PM, Alexander Graf <agraf@suse.de> wrote:

On 04/01/2015 10:15 AM, Jason Wang wrote:

This patch increases the maximum number of virtqueues for pci from 64
to 513. This will allow booting a virtio-net-pci device with 256 queue
pairs.

...

* configuration space */
#define VIRTIO_PCI_CONFIG_SIZE(dev) VIRTIO_PCI_CONFIG_OFF(msix_enabled(dev))
-#define VIRTIO_PCI_QUEUE_MAX 64
+#define VIRTIO_PCI_QUEUE_MAX 513

513 is an interesting number. Any particular reason for it? Maybe this was mentioned before and I just missed it ;)

quite
                large, too. I thought multiple queue pairs were useful

to
                split the load for multicore machines, but targeting VMs
                with

up
                  to 256 cores (and presumably an equal number in the
                  host)

seems
                  really forward looking.