netdev - Re: [PATCH net-next v3 5/7] net: devmem: add ring parameter filtering

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Message-ID: <CAHS8izNwnBnZf6P0WtAcg+MjmaxXDZ++kYit8_Ac8r6y=cDMAQ@mail.gmail.com>
Date: Thu, 3 Oct 2024 11:29:29 -0700
From: Mina Almasry <almasrymina@...gle.com>
To: Taehee Yoo <ap420073@...il.com>
Cc: davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com, 
	edumazet@...gle.com, netdev@...r.kernel.org, linux-doc@...r.kernel.org, 
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	kory.maincent@...tlin.com, andrew@...n.ch, maxime.chevallier@...tlin.com, 
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	paul.greenwalt@...el.com, rrameshbabu@...dia.com, idosch@...dia.com, 
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	aleksander.lobakin@...el.com, dw@...idwei.uk, sridhar.samudrala@...el.com, 
	bcreeley@....com
Subject: Re: [PATCH net-next v3 5/7] net: devmem: add ring parameter filtering

On Thu, Oct 3, 2024 at 9:07 AM Taehee Yoo <ap420073@...il.com> wrote:
>
> If driver doesn't support ring parameter or tcp-data-split configuration
> is not sufficient, the devmem should not be set up.
> Before setup the devmem, tcp-data-split should be ON and
> tcp-data-split-thresh value should be 0.
>
> Signed-off-by: Taehee Yoo <ap420073@...il.com>
> ---
>
> v3:
>  - Patch added.
>
>  net/core/devmem.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
>
> diff --git a/net/core/devmem.c b/net/core/devmem.c
> index 11b91c12ee11..a9e9b15028e0 100644
> --- a/net/core/devmem.c
> +++ b/net/core/devmem.c
> @@ -8,6 +8,8 @@
>   */
>
>  #include <linux/dma-buf.h>
> +#include <linux/ethtool.h>
> +#include <linux/ethtool_netlink.h>
>  #include <linux/genalloc.h>
>  #include <linux/mm.h>
>  #include <linux/netdevice.h>
> @@ -131,6 +133,8 @@ int net_devmem_bind_dmabuf_to_queue(struct net_device *dev, u32 rxq_idx,
>                                     struct net_devmem_dmabuf_binding *binding,
>                                     struct netlink_ext_ack *extack)
>  {
> +       struct kernel_ethtool_ringparam kernel_ringparam = {};
> +       struct ethtool_ringparam ringparam = {};
>         struct netdev_rx_queue *rxq;
>         u32 xa_idx;
>         int err;
> @@ -146,6 +150,20 @@ int net_devmem_bind_dmabuf_to_queue(struct net_device *dev, u32 rxq_idx,
>                 return -EEXIST;
>         }
>
> +       if (!dev->ethtool_ops->get_ringparam) {
> +               NL_SET_ERR_MSG(extack, "can't get ringparam");
> +               return -EINVAL;
> +       }
> +
> +       dev->ethtool_ops->get_ringparam(dev, &ringparam,
> +                                       &kernel_ringparam, extack);
> +       if (kernel_ringparam.tcp_data_split != ETHTOOL_TCP_DATA_SPLIT_ENABLED ||

The way I had set this up is that the driver checks whether header
split is enabled, and only sets PP_FLAG_ALLOW_UNREADABLE_NETMEM if it
is. Then core detects that the driver did not allow unreadable netmem
and it fails that way.

This check is redundant with that. I'm not 100% opposed to redundant
checks. Maybe they will add some reliability, but also maybe they will
be confusing to check the same thing essentially in 2 places.

Is the PP_FLAG_ALLOW_UNREADABLE_NETMEM trick not sufficient for you?

> +           kernel_ringparam.tcp_data_split_thresh) {
> +               NL_SET_ERR_MSG(extack,
> +                              "tcp-header-data-split is disabled or threshold is not zero");
> +               return -EINVAL;
> +       }
> +
>  #ifdef CONFIG_XDP_SOCKETS
>         if (rxq->pool) {
>                 NL_SET_ERR_MSG(extack, "designated queue already in use by AF_XDP");
> --
> 2.34.1
>


-- 
Thanks,
Mina