linux-kernel - RE: [EXTERNAL] Re: [PATCH V2,net-next, 1/2] net: mana: Add support for coalesced RX packets on CQE

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Message-ID:
 <SA3PR21MB3867BAD6022A1CAE2AC9E202CA81A@SA3PR21MB3867.namprd21.prod.outlook.com>
Date: Mon, 12 Jan 2026 21:01:59 +0000
From: Haiyang Zhang <haiyangz@...rosoft.com>
To: Jakub Kicinski <kuba@...nel.org>, Haiyang Zhang
	<haiyangz@...ux.microsoft.com>
CC: "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>, KY Srinivasan
	<kys@...rosoft.com>, Wei Liu <wei.liu@...nel.org>, Dexuan Cui
	<DECUI@...rosoft.com>, Long Li <longli@...rosoft.com>, Andrew Lunn
	<andrew+netdev@...n.ch>, "David S. Miller" <davem@...emloft.net>, Eric
 Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Konstantin
 Taranov <kotaranov@...rosoft.com>, Simon Horman <horms@...nel.org>, Erni Sri
 Satya Vennela <ernis@...ux.microsoft.com>, Shradha Gupta
	<shradhagupta@...ux.microsoft.com>, Saurabh Sengar
	<ssengar@...ux.microsoft.com>, Aditya Garg <gargaditya@...ux.microsoft.com>,
	Dipayaan Roy <dipayanroy@...ux.microsoft.com>, Shiraz Saleem
	<shirazsaleem@...rosoft.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-rdma@...r.kernel.org"
	<linux-rdma@...r.kernel.org>, Paul Rosswurm <paulros@...rosoft.com>
Subject: RE: [EXTERNAL] Re: [PATCH V2,net-next, 1/2] net: mana: Add support
 for coalesced RX packets on CQE



> -----Original Message-----
> From: Jakub Kicinski <kuba@...nel.org>
> Sent: Friday, January 9, 2026 8:56 PM
> To: Haiyang Zhang <haiyangz@...ux.microsoft.com>
> Cc: linux-hyperv@...r.kernel.org; netdev@...r.kernel.org; KY Srinivasan
> <kys@...rosoft.com>; Haiyang Zhang <haiyangz@...rosoft.com>; Wei Liu
> <wei.liu@...nel.org>; Dexuan Cui <DECUI@...rosoft.com>; Long Li
> <longli@...rosoft.com>; Andrew Lunn <andrew+netdev@...n.ch>; David S.
> Miller <davem@...emloft.net>; Eric Dumazet <edumazet@...gle.com>; Paolo
> Abeni <pabeni@...hat.com>; Konstantin Taranov <kotaranov@...rosoft.com>;
> Simon Horman <horms@...nel.org>; Erni Sri Satya Vennela
> <ernis@...ux.microsoft.com>; Shradha Gupta
> <shradhagupta@...ux.microsoft.com>; Saurabh Sengar
> <ssengar@...ux.microsoft.com>; Aditya Garg
> <gargaditya@...ux.microsoft.com>; Dipayaan Roy
> <dipayanroy@...ux.microsoft.com>; Shiraz Saleem
> <shirazsaleem@...rosoft.com>; linux-kernel@...r.kernel.org; linux-
> rdma@...r.kernel.org; Paul Rosswurm <paulros@...rosoft.com>
> Subject: [EXTERNAL] Re: [PATCH V2,net-next, 1/2] net: mana: Add support
> for coalesced RX packets on CQE
> 
> On Tue,  6 Jan 2026 12:46:46 -0800 Haiyang Zhang wrote:
> > From: Haiyang Zhang <haiyangz@...rosoft.com>
> >
> > Our NIC can have up to 4 RX packets on 1 CQE. To support this feature,
> > check and process the type CQE_RX_COALESCED_4. The default setting is
> > disabled, to avoid possible regression on latency.
> >
> > And add ethtool handler to switch this feature. To turn it on, run:
> >   ethtool -C <nic> rx-frames 4
> > To turn it off:
> >   ethtool -C <nic> rx-frames 1
> 
> Exposing just rx frame count, and only two values is quite unusual.
> Please explain in more detail the coalescing logic of the device.
Our NIC device only supports coalescing on RX. And when it's disabled each
RX CQE indicates 1 RX packet; when enabled each RX CQE indicates up to 4 packets.


> 
> > @@ -2079,14 +2081,10 @@ static void mana_process_rx_cqe(struct mana_rxq
> *rxq, struct mana_cq *cq,
> >  		return;
> >  	}
> >
> > -	pktlen = oob->ppi[0].pkt_len;
> > -
> > -	if (pktlen == 0) {
> > -		/* data packets should never have packetlength of zero */
> > -		netdev_err(ndev, "RX pkt len=0, rq=%u, cq=%u, rxobj=0x%llx\n",
> > -			   rxq->gdma_id, cq->gdma_id, rxq->rxobj);
> > +nextpkt:
> > +	pktlen = oob->ppi[i].pkt_len;
> > +	if (pktlen == 0)
> >  		return;
> > -	}
> >
> >  	curr = rxq->buf_index;
> >  	rxbuf_oob = &rxq->rx_oobs[curr];
> > @@ -2097,12 +2095,15 @@ static void mana_process_rx_cqe(struct mana_rxq
> *rxq, struct mana_cq *cq,
> >  	/* Unsuccessful refill will have old_buf == NULL.
> >  	 * In this case, mana_rx_skb() will drop the packet.
> >  	 */
> > -	mana_rx_skb(old_buf, old_fp, oob, rxq);
> > +	mana_rx_skb(old_buf, old_fp, oob, rxq, i);
> >
> >  drop:
> >  	mana_move_wq_tail(rxq->gdma_rq, rxbuf_oob->wqe_inf.wqe_size_in_bu);
> >
> >  	mana_post_pkt_rxq(rxq);
> > +
> > +	if (coalesced && (++i < MANA_RXCOMP_OOB_NUM_PPI))
> > +		goto nextpkt;
> 
> Please code this up as a loop. Using gotos for control flow other than
> to jump to error handling epilogues is a poor coding practice (see the
> kernel coding style).
Will do.

> 
> > +static int mana_set_coalesce(struct net_device *ndev,
> > +			     struct ethtool_coalesce *ec,
> > +			     struct kernel_ethtool_coalesce *kernel_coal,
> > +			     struct netlink_ext_ack *extack)
> > +{
> > +	struct mana_port_context *apc = netdev_priv(ndev);
> > +	u8 saved_cqe_coalescing_enable;
> > +	int err;
> > +
> > +	if (ec->rx_max_coalesced_frames != 1 &&
> > +	    ec->rx_max_coalesced_frames != MANA_RXCOMP_OOB_NUM_PPI) {
> > +		NL_SET_ERR_MSG_FMT(extack,
> > +				   "rx-frames must be 1 or %u, got %u",
> > +				   MANA_RXCOMP_OOB_NUM_PPI,
> > +				   ec->rx_max_coalesced_frames);
> > +		return -EINVAL;
> > +	}
> > +
> > +	saved_cqe_coalescing_enable = apc->cqe_coalescing_enable;
> > +	apc->cqe_coalescing_enable =
> > +		ec->rx_max_coalesced_frames == MANA_RXCOMP_OOB_NUM_PPI;
> > +
> > +	if (!apc->port_is_up)
> > +		return 0;
> > +
> > +	err = mana_config_rss(apc, TRI_STATE_TRUE, false, false);
> > +
> 
> unnecessary empty line
Will rm.

> 
> > +	if (err) {
> > +		netdev_err(ndev, "Set rx-frames to %u failed:%d\n",
> > +			   ec->rx_max_coalesced_frames, err);
> > +		NL_SET_ERR_MSG_FMT(extack, "Set rx-frames to %u failed",
> > +				   ec->rx_max_coalesced_frames);
> 
> These messages are both pointless. If HW communication has failed
> presumably there will already be an error in the logs. The extack
> gives the user no information they wouldn't already have.
Will rm.

Thanks,
- Haiyang