netdev - Re: [RFC net-next 19/22] eth: bnxt: use queue op config validate

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Message-ID: <yjqlfsbjbaz4l72fmw6arm6expsq3qxxkxlwzkywrcr3o4rhdq@bfuqhyjlp3mo>
Date: Wed, 23 Apr 2025 14:24:56 +0000
From: Dragos Tatulea <dtatulea@...dia.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com, 
	pabeni@...hat.com, andrew+netdev@...n.ch, horms@...nel.org, donald.hunter@...il.com, 
	sdf@...ichev.me, almasrymina@...gle.com, dw@...idwei.uk, asml.silence@...il.com, 
	ap420073@...il.com, jdamato@...tly.com, michael.chan@...adcom.com
Subject: Re: [RFC net-next 19/22] eth: bnxt: use queue op config validate

On Wed, Apr 23, 2025 at 06:46:53AM -0700, Jakub Kicinski wrote:
> On Wed, 23 Apr 2025 10:00:01 +0000 Dragos Tatulea wrote:
> > > +static int
> > > +bnxt_queue_cfg_validate(struct net_device *dev, int idx,
> > > +			struct netdev_queue_config *qcfg,
> > > +			struct netlink_ext_ack *extack)
> > > +{
> > > +	struct bnxt *bp = netdev_priv(dev);
> > > +
> > > +	/* Older chips need MSS calc so rx_buf_len is not supported,
> > > +	 * but we don't set queue ops for them so we should never get here.
> > > +	 */
> > > +	if (qcfg->rx_buf_len != bp->rx_page_size &&
> > > +	    !(bp->flags & BNXT_FLAG_CHIP_P5_PLUS)) {
> > > +		NL_SET_ERR_MSG_MOD(extack, "changing rx-buf-len not supported");
> > > +		return -EINVAL;
> > > +	}
> > > +
> > > +	if (!is_power_of_2(qcfg->rx_buf_len)) {
> > > +		NL_SET_ERR_MSG_MOD(extack, "rx-buf-len is not power of 2");
> > > +		return -ERANGE;
> > > +	}
> > > +	if (qcfg->rx_buf_len < BNXT_RX_PAGE_SIZE ||
> > > +	    qcfg->rx_buf_len > BNXT_MAX_RX_PAGE_SIZE) {
> > > +		NL_SET_ERR_MSG_MOD(extack, "rx-buf-len out of range");
> > > +		return -ERANGE;
> > > +	}
> > > +	return 0;
> > > +}
> > > +  
> > HDS off and rx_buf_len > 4K seems to be accepted. Is this inteded?
> 
> For bnxt rx_buf_len only applies to the "payload buffers".
> I should document that, and retest with XDP. 
> 
> I posted a doc recently with a "design guide" for API interfaces, 
> it said:
> 
>   Visibility
>   ==========
> 
>   To simplify the implementations configuration parameters of disabled features
>   do not have to be hidden, or inaccessible.
> 
> Which I intended to mean that configuring something that isn't enabled
> is okay. IIRC we also don't reject setting hds threshold if hds is off.
>
> Hope I understood what you're getting at.
My bad. My question was too terse and not generic enough. What I meant
to ask was:

With this new API, should drivers be allowed to use high order pages
from the page_pool regardless of HDS mode? From your reply I understand
that it is a yes.

Thanks,
Dragos