linux-kernel - RE: [PATCH v6 RESEND net-next 1/5] net: enetc: add Rx checksum offload for i.MX95 ENETC

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID:
 <PAXPR04MB85107FD857F1AB33BBE4F70988312@PAXPR04MB8510.eurprd04.prod.outlook.com>
Date: Fri, 6 Dec 2024 12:45:02 +0000
From: Wei Fang <wei.fang@....com>
To: Simon Horman <horms@...nel.org>
CC: Claudiu Manoil <claudiu.manoil@....com>, Vladimir Oltean
	<vladimir.oltean@....com>, Clark Wang <xiaoning.wang@....com>,
	"andrew+netdev@...n.ch" <andrew+netdev@...n.ch>, "davem@...emloft.net"
	<davem@...emloft.net>, "edumazet@...gle.com" <edumazet@...gle.com>,
	"kuba@...nel.org" <kuba@...nel.org>, "pabeni@...hat.com" <pabeni@...hat.com>,
	Frank Li <frank.li@....com>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "imx@...ts.linux.dev" <imx@...ts.linux.dev>
Subject: RE: [PATCH v6 RESEND net-next 1/5] net: enetc: add Rx checksum
 offload for i.MX95 ENETC

> -----Original Message-----
> From: Simon Horman <horms@...nel.org>
> Sent: 2024年12月6日 20:31
> To: Wei Fang <wei.fang@....com>
> Cc: Claudiu Manoil <claudiu.manoil@....com>; Vladimir Oltean
> <vladimir.oltean@....com>; Clark Wang <xiaoning.wang@....com>;
> andrew+netdev@...n.ch; davem@...emloft.net; edumazet@...gle.com;
> kuba@...nel.org; pabeni@...hat.com; Frank Li <frank.li@....com>;
> netdev@...r.kernel.org; linux-kernel@...r.kernel.org; imx@...ts.linux.dev
> Subject: Re: [PATCH v6 RESEND net-next 1/5] net: enetc: add Rx checksum
> offload for i.MX95 ENETC
> 
> On Fri, Dec 06, 2024 at 10:33:15AM +0000, Wei Fang wrote:
> > > -----Original Message-----
> > > From: Simon Horman <horms@...nel.org>
> > > Sent: 2024年12月6日 17:23
> > > To: Wei Fang <wei.fang@....com>
> > > Cc: Claudiu Manoil <claudiu.manoil@....com>; Vladimir Oltean
> > > <vladimir.oltean@....com>; Clark Wang <xiaoning.wang@....com>;
> > > andrew+netdev@...n.ch; davem@...emloft.net; edumazet@...gle.com;
> > > kuba@...nel.org; pabeni@...hat.com; Frank Li <frank.li@....com>;
> > > netdev@...r.kernel.org; linux-kernel@...r.kernel.org; imx@...ts.linux.dev
> > > Subject: Re: [PATCH v6 RESEND net-next 1/5] net: enetc: add Rx checksum
> > > offload for i.MX95 ENETC
> > >
> > > On Wed, Dec 04, 2024 at 01:29:28PM +0800, Wei Fang wrote:
> > > > ENETC rev 4.1 supports TCP and UDP checksum offload for receive, the bit
> > > > 108 of the Rx BD will be set if the TCP/UDP checksum is correct. Since
> > > > this capability is not defined in register, the rx_csum bit is added to
> > > > struct enetc_drvdata to indicate whether the device supports Rx
> checksum
> > > > offload.
> > > >
> > > > Signed-off-by: Wei Fang <wei.fang@....com>
> > > > Reviewed-by: Frank Li <Frank.Li@....com>
> > > > Reviewed-by: Claudiu Manoil <claudiu.manoil@....com>
> > > > ---
> > > > v2: no changes
> > > > v3: no changes
> > > > v4: no changes
> > > > v5: no changes
> > > > v6: no changes
> > > > ---
> > > >  drivers/net/ethernet/freescale/enetc/enetc.c       | 14
> ++++++++++----
> > > >  drivers/net/ethernet/freescale/enetc/enetc.h       |  2 ++
> > > >  drivers/net/ethernet/freescale/enetc/enetc_hw.h    |  2 ++
> > > >  .../net/ethernet/freescale/enetc/enetc_pf_common.c |  3 +++
> > > >  4 files changed, 17 insertions(+), 4 deletions(-)
> > > >
> > > > diff --git a/drivers/net/ethernet/freescale/enetc/enetc.c
> > > b/drivers/net/ethernet/freescale/enetc/enetc.c
> > > > index 35634c516e26..3137b6ee62d3 100644
> > > > --- a/drivers/net/ethernet/freescale/enetc/enetc.c
> > > > +++ b/drivers/net/ethernet/freescale/enetc/enetc.c
> > > > @@ -1011,10 +1011,15 @@ static void enetc_get_offloads(struct
> enetc_bdr
> > > *rx_ring,
> > > >
> > > >  	/* TODO: hashing */
> > > >  	if (rx_ring->ndev->features & NETIF_F_RXCSUM) {
> > > > -		u16 inet_csum = le16_to_cpu(rxbd->r.inet_csum);
> > > > -
> > > > -		skb->csum = csum_unfold((__force
> __sum16)~htons(inet_csum));
> > > > -		skb->ip_summed = CHECKSUM_COMPLETE;
> > > > +		if (priv->active_offloads & ENETC_F_RXCSUM &&
> > > > +		    le16_to_cpu(rxbd->r.flags) &
> ENETC_RXBD_FLAG_L4_CSUM_OK)
> > > {
> > > > +			skb->ip_summed = CHECKSUM_UNNECESSARY;
> > > > +		} else {
> > > > +			u16 inet_csum = le16_to_cpu(rxbd->r.inet_csum);
> > > > +
> > > > +			skb->csum = csum_unfold((__force
> __sum16)~htons(inet_csum));
> > > > +			skb->ip_summed = CHECKSUM_COMPLETE;
> > > > +		}
> > > >  	}
> > >
> > > Hi Wei,
> > >
> > > I am wondering about the relationship between the above and
> > > hardware support for CHECKSUM_COMPLETE.
> > >
> > > Prior to this patch CHECKSUM_COMPLETE was always used, which seems
> > > desirable. But with this patch, CHECKSUM_UNNECESSARY is conditionally
> used.
> > >
> > > If those cases don't work with CHECKSUM_COMPLETE then is this a
> bug-fix?
> > >
> > > Or, alternatively, if those cases do work with CHECKSUM_COMPLETE, then
> > > I'm unsure why this change is necessary or desirable. It's my understanding
> > > that from the Kernel's perspective CHECKSUM_COMPLETE is preferable to
> > > CHECKSUM_UNNECESSARY.
> > >
> > > ...
> >
> > Rx checksum offload is a new feature of ENETC v4. We would like to exploit
> this
> > capability of the hardware to save CPU cycles in calculating and verifying
> checksum.
> >
> 
> Understood, but CHECKSUM_UNNECESSARY is usually the preferred option as
> it
> is more flexible, e.g. allowing low-cost calculation of inner checksums
> in the presence of encapsulation.

I think you mean 'CHECKSUM_COMPLETE' is the preferred option. But there is no
strong reason against using CHECKSUM_UNNECESSARY. So I hope to keep this patch.