Michael,
Thanks for the fix.
There was another question which was lost in the thread.
I am testing virtio-net in two ways:
Old -net interface:
-net tap,ifname=tap0,script=qemu-ifup.sh \
-net nic,model=virtio,addr=0:0:0
(qemu) info network
hub 0
\ virtio-net-pci.0:
index=0,type=nic,model=virtio-net-pci,macaddr=52:54:00:12:34:56
\ tap.0:
index=0,type=tap,ifname=tap0,script=qemu-ifup.sh,downscript=/etc/qemu-ifdown
New -netdev interface:
-netdev tap,id=tapnet,ifname=tap0,script=qemu-ifup.sh \
-device virtio-net-pci,netdev=tapnet,addr=0.0
(qemu) info network
virtio-net-pci.0:
index=0,type=nic,model=virtio-net-pci,macaddr=52:54:00:12:34:56
\ tapnet:
index=0,type=tap,ifname=tap0,script=qemu-ifup.sh,downscript=/etc/qemu-ifdown
I get very different virtio0 device features and speed (70MB/s vs.
700MB/s). I guess somehow the "hub 0" is responsible but there is no way to
avoid it.
Is there any way to speed up the virtio-net using the old -net interface?
On 06/03/13 21:31, Michael S. Tsirkin wrote:
On Wed, Mar 06, 2013 at 09:57:40AM +1100, Alexey Kardashevskiy wrote:
On 06/03/13 01:23, Michael S. Tsirkin wrote:
On Wed, Mar 06, 2013 at 12:21:47AM +1100, Alexey Kardashevskiy wrote:
On 05/03/13 23:56, Michael S. Tsirkin wrote:
The patch f56a12475ff1b8aa61210d08522c3c8aaf0e2648 "vhost: backend
masking support" breaks virtio-net + vhost=on on PPC64 platform.
The problem command line is:
1) -netdev tap,id=tapnet,ifname=tap0,script=qemu-ifup.sh,vhost=on \
-device virtio-net-pci,netdev=tapnet,addr=0.0 \
I think the issue is irqfd in not supported on kvm ppc.
How can I make sure this is the case? Some work has been done there
recently but midnight is quite late to figure this out :)
Look in virtio_pci_set_guest_notifiers, what is the
value of with_irqfd?
bool with_irqfd = msix_enabled(&proxy->pci_dev) &&
kvm_msi_via_irqfd_enabled();
Also check what each of the values in the expression above is.
Yes, ppc does not have irqfd as kvm_msi_via_irqfd_enabled() returned "false".
Could you please check this:
+ /* If guest supports masking, set up irqfd now.
+ * Otherwise, delay until unmasked in the frontend.
+ */
+ if (proxy->vdev->guest_notifier_mask) {
+ ret = kvm_virtio_pci_irqfd_use(proxy, queue_no, vector);
+ if (ret < 0) {
+ kvm_virtio_pci_vq_vector_release(proxy, vector);
+ goto undo;
+ }
+ }
Could you please add a printf before "undo" and check whether the
error path above is triggered?
Checked, it is not triggered.
--
Alexey
I think I get it.
Does the following help (probably not the right thing to do, but just
for testing):
It did not compile (no "queue_no") :) I changed it a bit and now
vhost=on works fine:
diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
index a869f53..df1e443 100644
--- a/hw/virtio-pci.c
+++ b/hw/virtio-pci.c
@@ -798,6 +798,10 @@ static int
virtio_pci_set_guest_notifiers(DeviceState *d, int nvqs, bool
assign)
if (r < 0) {
goto assign_error;
}
+
+ if (!with_irqfd && proxy->vdev->guest_notifier_mask) {
+ proxy->vdev->guest_notifier_mask(proxy->vdev, n, !assign);
+ }
}
/* Must set vector notifier after guest notifier has been assigned */
I see, OK, the issue is that vhost now starts in a masked state
and no one unmasks it. While the patch will work I think,
it does not benefit from backend masking, the right thing
to do is to add mask notifiers, like what the irqfd path does.
Will look into this, thanks.
--
Alexey
