[PATCH AUTOSEL 4.19 204/205] s390/qeth: limit csum offload erratum to L3 devices

[PATCH AUTOSEL 4.19 204/205] s390/qeth: limit csum offload erratum to L3 devices

[Sasha Levin]

From: Julian Wiedmann <jwi@linux.ibm.com>

[ Upstream commit f231dc9dbd789b0f98a15941e3cebedb4ad72ad5 ]

Combined L3+L4 csum offload is only required for some L3 HW. So for
L2 devices, don't offload the IP header csum calculation.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Reference-ID: JUP 394553
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/s390/net/qeth_core.h    | 5 -----
 drivers/s390/net/qeth_l3_main.c | 5 +++++
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/s390/net/qeth_core.h b/drivers/s390/net/qeth_core.h
index b2657582cfcfd..41a2f901ccee5 100644
--- a/drivers/s390/net/qeth_core.h
+++ b/drivers/s390/net/qeth_core.h
@@ -902,11 +902,6 @@ static inline void qeth_tx_csum(struct sk_buff *skb, u8 *flags, int ipv)
 	if ((ipv == 4 && ip_hdr(skb)->protocol == IPPROTO_UDP) ||
 	    (ipv == 6 && ipv6_hdr(skb)->nexthdr == IPPROTO_UDP))
 		*flags |= QETH_HDR_EXT_UDP;
-	if (ipv == 4) {
-		/* some HW requires combined L3+L4 csum offload: */
-		*flags |= QETH_HDR_EXT_CSUM_HDR_REQ;
-		ip_hdr(skb)->check = 0;
-	}
 }
 
 static inline void qeth_put_buffer_pool_entry(struct qeth_card *card,
diff --git a/drivers/s390/net/qeth_l3_main.c b/drivers/s390/net/qeth_l3_main.c
index 9c5e801b3f6cb..c60660cb5a031 100644
--- a/drivers/s390/net/qeth_l3_main.c
+++ b/drivers/s390/net/qeth_l3_main.c
@@ -2054,6 +2054,11 @@ static void qeth_l3_fill_header(struct qeth_card *card, struct qeth_hdr *hdr,
 
 	if (!skb_is_gso(skb) && skb->ip_summed == CHECKSUM_PARTIAL) {
 		qeth_tx_csum(skb, &hdr->hdr.l3.ext_flags, ipv);
+		/* some HW requires combined L3+L4 csum offload: */
+		if (ipv == 4) {
+			hdr->hdr.l3.ext_flags |= QETH_HDR_EXT_CSUM_HDR_REQ;
+			ip_hdr(skb)->check = 0;
+		}
 		if (card->options.performance_stats)
 			card->perf_stats.tx_csum++;
 	}
-- 
2.20.1

Re: [PATCH AUTOSEL 4.19 204/205] s390/qeth: limit csum offload erratum to L3 devices

[Julian Wiedmann]

On 08.11.19 12:37, Sasha Levin wrote:
> From: Julian Wiedmann <jwi@linux.ibm.com>
> 
> [ Upstream commit f231dc9dbd789b0f98a15941e3cebedb4ad72ad5 ]
> 
> Combined L3+L4 csum offload is only required for some L3 HW. So for
> L2 devices, don't offload the IP header csum calculation.
> 

NACK, this has no relevance for stable.


> Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
> Reference-ID: JUP 394553
> Signed-off-by: David S. Miller <davem@davemloft.net>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
>  drivers/s390/net/qeth_core.h    | 5 -----
>  drivers/s390/net/qeth_l3_main.c | 5 +++++
>  2 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/s390/net/qeth_core.h b/drivers/s390/net/qeth_core.h
> index b2657582cfcfd..41a2f901ccee5 100644
> --- a/drivers/s390/net/qeth_core.h
> +++ b/drivers/s390/net/qeth_core.h
> @@ -902,11 +902,6 @@ static inline void qeth_tx_csum(struct sk_buff *skb, u8 *flags, int ipv)
>  	if ((ipv == 4 && ip_hdr(skb)->protocol == IPPROTO_UDP) ||
>  	    (ipv == 6 && ipv6_hdr(skb)->nexthdr == IPPROTO_UDP))
>  		*flags |= QETH_HDR_EXT_UDP;
> -	if (ipv == 4) {
> -		/* some HW requires combined L3+L4 csum offload: */
> -		*flags |= QETH_HDR_EXT_CSUM_HDR_REQ;
> -		ip_hdr(skb)->check = 0;
> -	}
>  }
>  
>  static inline void qeth_put_buffer_pool_entry(struct qeth_card *card,
> diff --git a/drivers/s390/net/qeth_l3_main.c b/drivers/s390/net/qeth_l3_main.c
> index 9c5e801b3f6cb..c60660cb5a031 100644
> --- a/drivers/s390/net/qeth_l3_main.c
> +++ b/drivers/s390/net/qeth_l3_main.c
> @@ -2054,6 +2054,11 @@ static void qeth_l3_fill_header(struct qeth_card *card, struct qeth_hdr *hdr,
>  
>  	if (!skb_is_gso(skb) && skb->ip_summed == CHECKSUM_PARTIAL) {
>  		qeth_tx_csum(skb, &hdr->hdr.l3.ext_flags, ipv);
> +		/* some HW requires combined L3+L4 csum offload: */
> +		if (ipv == 4) {
> +			hdr->hdr.l3.ext_flags |= QETH_HDR_EXT_CSUM_HDR_REQ;
> +			ip_hdr(skb)->check = 0;
> +		}
>  		if (card->options.performance_stats)
>  			card->perf_stats.tx_csum++;
>  	}
> 

Re: [PATCH AUTOSEL 4.19 204/205] s390/qeth: limit csum offload erratum to L3 devices

[Sasha Levin]

On Fri, Nov 08, 2019 at 12:50:24PM +0100, Julian Wiedmann wrote:
>On 08.11.19 12:37, Sasha Levin wrote:
>> From: Julian Wiedmann <jwi@linux.ibm.com>
>>
>> [ Upstream commit f231dc9dbd789b0f98a15941e3cebedb4ad72ad5 ]
>>
>> Combined L3+L4 csum offload is only required for some L3 HW. So for
>> L2 devices, don't offload the IP header csum calculation.
>>
>
>NACK, this has no relevance for stable.

Sure, I'll drop it.

Do you have an idea why the centos and ubuntu folks might have
backported this commit into their kernels?

-- 
Thanks,
Sasha

Re: [PATCH AUTOSEL 4.19 204/205] s390/qeth: limit csum offload erratum to L3 devices

[Julian Wiedmann]

On 08.11.19 13:00, Sasha Levin wrote:
> On Fri, Nov 08, 2019 at 12:50:24PM +0100, Julian Wiedmann wrote:
>> On 08.11.19 12:37, Sasha Levin wrote:
>>> From: Julian Wiedmann <jwi@linux.ibm.com>
>>>
>>> [ Upstream commit f231dc9dbd789b0f98a15941e3cebedb4ad72ad5 ]
>>>
>>> Combined L3+L4 csum offload is only required for some L3 HW. So for
>>> L2 devices, don't offload the IP header csum calculation.
>>>
>>
>> NACK, this has no relevance for stable.
> 
> Sure, I'll drop it.
> 
> Do you have an idea why the centos and ubuntu folks might have
> backported this commit into their kernels?
> 

No clue, I trust they have their own reasons.

Re: [PATCH AUTOSEL 4.19 204/205] s390/qeth: limit csum offload erratum to L3 devices

[Greg KH]

On Fri, Nov 08, 2019 at 01:16:26PM +0100, Julian Wiedmann wrote:
> On 08.11.19 13:00, Sasha Levin wrote:
> > On Fri, Nov 08, 2019 at 12:50:24PM +0100, Julian Wiedmann wrote:
> >> On 08.11.19 12:37, Sasha Levin wrote:
> >>> From: Julian Wiedmann <jwi@linux.ibm.com>
> >>>
> >>> [ Upstream commit f231dc9dbd789b0f98a15941e3cebedb4ad72ad5 ]
> >>>
> >>> Combined L3+L4 csum offload is only required for some L3 HW. So for
> >>> L2 devices, don't offload the IP header csum calculation.
> >>>
> >>
> >> NACK, this has no relevance for stable.
> > 
> > Sure, I'll drop it.
> > 
> > Do you have an idea why the centos and ubuntu folks might have
> > backported this commit into their kernels?
> > 
> 
> No clue, I trust they have their own reasons.
> 

I cant see centos backporting anything unless they were asked to do so.
And this really looks like a "bugfix" to me, why isn't this relevant for
any older kernel versions?

thanks,

greg k-h

Re: [PATCH AUTOSEL 4.19 204/205] s390/qeth: limit csum offload erratum to L3 devices

[David Miller]

From: Greg KH <gregkh@linuxfoundation.org>
Date: Fri, 8 Nov 2019 13:34:16 +0100

> On Fri, Nov 08, 2019 at 01:16:26PM +0100, Julian Wiedmann wrote:
>> On 08.11.19 13:00, Sasha Levin wrote:
>> > On Fri, Nov 08, 2019 at 12:50:24PM +0100, Julian Wiedmann wrote:
>> >> On 08.11.19 12:37, Sasha Levin wrote:
>> >>> From: Julian Wiedmann <jwi@linux.ibm.com>
>> >>>
>> >>> [ Upstream commit f231dc9dbd789b0f98a15941e3cebedb4ad72ad5 ]
>> >>>
>> >>> Combined L3+L4 csum offload is only required for some L3 HW. So for
>> >>> L2 devices, don't offload the IP header csum calculation.
>> >>>
>> >>
>> >> NACK, this has no relevance for stable.
>> > 
>> > Sure, I'll drop it.
>> > 
>> > Do you have an idea why the centos and ubuntu folks might have
>> > backported this commit into their kernels?
>> > 
>> 
>> No clue, I trust they have their own reasons.
>> 
> 
> I cant see centos backporting anything unless they were asked to do so.
> And this really looks like a "bugfix" to me, why isn't this relevant for
> any older kernel versions?

Yeah seriously, this looks entirely legit.

Re: [PATCH AUTOSEL 4.19 204/205] s390/qeth: limit csum offload erratum to L3 devices

[Julian Wiedmann]

On 08.11.19 20:35, David Miller wrote:
> From: Greg KH <gregkh@linuxfoundation.org>
> Date: Fri, 8 Nov 2019 13:34:16 +0100
> 
>> On Fri, Nov 08, 2019 at 01:16:26PM +0100, Julian Wiedmann wrote:
>>> On 08.11.19 13:00, Sasha Levin wrote:
>>>> On Fri, Nov 08, 2019 at 12:50:24PM +0100, Julian Wiedmann wrote:
>>>>> On 08.11.19 12:37, Sasha Levin wrote:
>>>>>> From: Julian Wiedmann <jwi@linux.ibm.com>
>>>>>>
>>>>>> [ Upstream commit f231dc9dbd789b0f98a15941e3cebedb4ad72ad5 ]
>>>>>>
>>>>>> Combined L3+L4 csum offload is only required for some L3 HW. So for
>>>>>> L2 devices, don't offload the IP header csum calculation.
>>>>>>
>>>>>
>>>>> NACK, this has no relevance for stable.
>>>>
>>>> Sure, I'll drop it.
>>>>
>>>> Do you have an idea why the centos and ubuntu folks might have
>>>> backported this commit into their kernels?
>>>>
>>>
>>> No clue, I trust they have their own reasons.
>>>
>>
>> I cant see centos backporting anything unless they were asked to do so.
>> And this really looks like a "bugfix" to me, why isn't this relevant for
>> any older kernel versions?
> 
> Yeah seriously, this looks entirely legit.
> 

I can assure you this doesn't fix any actual bug, and there's zero user
impact from _not_ having this patch.