linux-kernel - Re: [PATCH net-next v5 3/4] virtio-net: Map NAPIs to queues

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Message-ID: <CACGkMEus3m5M5ecA4u7irKd-N0p0=ZjnAPanLk-YJgoB6jhgBA@mail.gmail.com>
Date: Fri, 28 Feb 2025 16:14:46 +0800
From: Jason Wang <jasowang@...hat.com>
To: Joe Damato <jdamato@...tly.com>
Cc: netdev@...r.kernel.org, mkarsten@...terloo.ca, 
	gerhard@...leder-embedded.com, xuanzhuo@...ux.alibaba.com, kuba@...nel.org, 
	mst@...hat.com, leiyang@...hat.com, Eugenio Pérez <eperezma@...hat.com>, 
	Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, 
	"open list:VIRTIO CORE AND NET DRIVERS" <virtualization@...ts.linux.dev>, open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next v5 3/4] virtio-net: Map NAPIs to queues

On Fri, Feb 28, 2025 at 2:50 AM Joe Damato <jdamato@...tly.com> wrote:
>
> Use netif_queue_set_napi to map NAPIs to queue IDs so that the mapping
> can be accessed by user apps. Note that the netif_queue_set_napi
> currently requires RTNL, so care must be taken to ensure RTNL is held on
> paths where this API might be reached.
>
> The paths in the driver where this API can be reached appear to be:
>
>   - ndo_open, ndo_close, which hold RTNL so no driver change is needed.
>   - rx_pause, rx_resume, tx_pause, tx_resume are reached either via
>     an ethtool ioctl or via XSK - neither path requires a driver change.
>   - power management paths (which call open and close), which have been
>     updated to hold/release RTNL.
>   - refill_work, which has been updated to hold RTNL.
>
> $ ethtool -i ens4 | grep driver
> driver: virtio_net
>
> $ sudo ethtool -L ens4 combined 4
>
> $ ./tools/net/ynl/pyynl/cli.py \
>        --spec Documentation/netlink/specs/netdev.yaml \
>        --dump queue-get --json='{"ifindex": 2}'
> [{'id': 0, 'ifindex': 2, 'napi-id': 8289, 'type': 'rx'},
>  {'id': 1, 'ifindex': 2, 'napi-id': 8290, 'type': 'rx'},
>  {'id': 2, 'ifindex': 2, 'napi-id': 8291, 'type': 'rx'},
>  {'id': 3, 'ifindex': 2, 'napi-id': 8292, 'type': 'rx'},
>  {'id': 0, 'ifindex': 2, 'type': 'tx'},
>  {'id': 1, 'ifindex': 2, 'type': 'tx'},
>  {'id': 2, 'ifindex': 2, 'type': 'tx'},
>  {'id': 3, 'ifindex': 2, 'type': 'tx'}]
>
> Note that virtio_net has TX-only NAPIs which do not have NAPI IDs, so
> the lack of 'napi-id' in the above output is expected.
>
> Signed-off-by: Joe Damato <jdamato@...tly.com>
> ---

Acked-by: Jason Wang <jasowang@...hat.com>

Thanks