Re: [PATCH v2 1/3] virtio_pci_modern: Allow non power of 2 sizes for virtqueues

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On 2023-03-12 a.m.1:46, Michael S. Tsirkin wrote:
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On Sat, Mar 11, 2023 at 05:25:04PM -0500, Feng Liu wrote:


On 2023-03-11 p.m.2:05, Michael S. Tsirkin wrote:
External email: Use caution opening links or attachments


On Fri, Mar 10, 2023 at 10:23:16AM -0500, Feng Liu wrote:


On 2023-03-10 a.m.8:36, Parav Pandit wrote:


From: Feng Liu <feliu@xxxxxxxxxx>
Sent: Friday, March 10, 2023 12:34 AM


- if (!is_power_of_2(num)) {
-         dev_warn(&vp_dev->pci_dev->dev, "bad queue size %u",
num);
-         return ERR_PTR(-EINVAL);
- }
-

The check is still valid for split q.
Maybe the right place for such a check is not the pci transport driver.
But layer below where split vs packed q knowledge resides and hence, power of 2 check can be omitted for packed vq.

Hi, Parav
      I think you are right, I checked the virtio spec, only packed virtqueue
can use queue size which is not power_of_2; so, I think the check can be
reserved only for split queue here, something like

struct virtio_device *vdev = &vp_dev->vdev;
if (!virtio_has_feature(vdev, VIRTIO_F_RING_PACKED)
   && !is_power_of_2(num)){
      dev_warn(&vp_dev->pci_dev->dev, "bad queue size %u", num);
      return ERR_PTR(-EINVAL);
}

I will fix it in next version

Hi, Michael and Jason
Do you have any comments on this?


Hmm good point. Which raises the question: so how did you test it then?

Hi Michael

I will construct a non power of 2 size packed virtqueue device to test
whether the driver is loaded successfully and whether the traffic is normal;
at the same time, I will also construct a non power of 2 size split
virtqueue device for testing to see if an warning is given and the driver is
loaded fail

The method of constructing the device, such as the reply steps in the
previous email

Okay but previously you said you tested ring sizes 100 and 200 with
iperf. How did you construct these?


Hi, Michael

After the driver has been successfully loaded, I will use iperf to test whether the network traffic is functioning properly. I will start the iperf server on the peer-end and the iperf client within the vm. I will then initiate a data transfer to perform the test.



--
MST


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