Re: [virtio-comment] [PATCH requirements 1/7] net-features: Add requirements document for release 1.4

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Jun 02, 2023 at 01:02:59AM +0300, Parav Pandit wrote:
> Add requirements document template for the virtio net features.
> 
> Add virtio net device counters visible to driver.
> 
> Signed-off-by: Parav Pandit <parav@nvidia.com>
> ---
>  net-workstream/features-1.4.md | 36 ++++++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
>  create mode 100644 net-workstream/features-1.4.md
> 
> diff --git a/net-workstream/features-1.4.md b/net-workstream/features-1.4.md
> new file mode 100644
> index 0000000..03b4eb3
> --- /dev/null
> +++ b/net-workstream/features-1.4.md
> @@ -0,0 +1,36 @@
> +# 1. Introduction
> +
> +This document describes the overall requirements for virtio net device
> +improvements for upcoming release 1.4. Some of these requirements are
> +interrelated and influence the interface design, hence reviewing them
> +together is desired while updating the virtio net interface.
> +
> +# 2. Summary
> +1. Device counters visible to the driver
> +
> +# 3. Requirements
> +## 3.1 Device counters
> +1. The driver should be able to query the device and/or per vq counters for
> +   debugging purpose using a control vq command.
> +2. The driver should be able to query which counters are supported using a
> +   control vq command.

why does it matter for requirements whether it's a control vq?


what matters is whether they have to be synchronized
with a given queue - I get it they don't have to.

> +3. If this device is migrated between two hosts, the driver should be able
> +   get the counter values in the destination host from where it was left
> +   off in the source host.

we don't cover migration currently don't see how this is a spec
rquirement. unless maybe it's justification for 4?
so maybe it means there needs to be a way to set counters?
so there's no need to mention migration - just that it
should be possible to move counters between devices.

> +4. If a virtio device is group member device, a group owner should be able
> +   to query all the counter attributes using the admin queue command which
> +   a virtio device will expose via a control vq to the driver.


this seems weirdly specific.
what is the actual requirement?


> +
> +### 3.1.1 Per receive queue counters
> +1. le64 rx_oversize_pkt_errors: Packet dropped due to receive packet being
> +    oversize than the buffer size

with mergeable buffers how does this differ from 2?

> +2. le64 rx_no_buffer_pkt_errors: Packet dropped due to unavailability of the
> +    buffer in the receive queue
> +3. le64 rx_gro_pkts: Packets treated as guest GSO sequence by the device

what does this mean exactly? packets before or after they are combined?

pls stick to device/driver terminology not guest/host

> +4. le64 rx_pkts: Total packets received by the device

including dropped ones or not?

> +
> +### 3.1.2 Per transmit queue counters
> +1. le64 tx_bad_desc_errors: Descriptors dropped by the device due to errors in
> +   descriptors

since when do we drop packets on error in descriptor?
we just as likely stall ...

> +2. le64 tx_gso_pkts: Packets send as host GSO sequence

same questions as gro

> +3. le64 tx_pkts: Total packets send by the device

sent

> -- 
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