From: Emil Berg <emil.berg@ericsson.com>
To: "Stephen Hemminger" <stephen@networkplumber.org>,
"Morten Brørup" <mb@smartsharesystems.com>
Cc: "bruce.richardson@intel.com" <bruce.richardson@intel.com>,
"dev@dpdk.org" <dev@dpdk.org>,
"stable@dpdk.org" <stable@dpdk.org>,
"bugzilla@dpdk.org" <bugzilla@dpdk.org>,
"hofors@lysator.liu.se" <hofors@lysator.liu.se>,
"olivier.matz@6wind.com" <olivier.matz@6wind.com>
Subject: RE: [PATCH v4] net: fix checksum with unaligned buffer
Date: Fri, 1 Jul 2022 04:11:17 +0000 [thread overview]
Message-ID: <AM8PR07MB7666AD7BF7B780CC5062C14598BD9@AM8PR07MB7666.eurprd07.prod.outlook.com> (raw)
In-Reply-To: <20220630104545.55d4e870@hermes.local>
> -----Original Message-----
> From: Stephen Hemminger <stephen@networkplumber.org>
> Sent: den 30 juni 2022 19:46
> To: Morten Brørup <mb@smartsharesystems.com>
> Cc: Emil Berg <emil.berg@ericsson.com>; bruce.richardson@intel.com;
> dev@dpdk.org; stable@dpdk.org; bugzilla@dpdk.org; hofors@lysator.liu.se;
> olivier.matz@6wind.com
> Subject: Re: [PATCH v4] net: fix checksum with unaligned buffer
>
> On Thu, 23 Jun 2022 14:39:00 +0200
> Morten Brørup <mb@smartsharesystems.com> wrote:
>
> > + /* if buffer is unaligned, keeping it byte order independent */
> > + if (unlikely(unaligned)) {
> > + uint16_t first = 0;
> > + if (unlikely(len == 0))
> > + return 0;
>
> Why is length == 0 unique to unaligned case?
>
> > + ((unsigned char *)&first)[1] = *(const unsigned
> char *)buf;
>
> Use a proper union instead of casting to avoid aliasing warnings.
>
> > + bsum += first;
> > + buf = RTE_PTR_ADD(buf, 1);
> > + len--;
> > + }
>
> Many CPU's (such as x86) won't care about alignment and therefore the
> extra code to handle this is not worth doing.
>
x86 does care about alignment. An example is the vmovdqa instruction, where 'a' stands for 'aligned'. The description in the link below says: "When the source or destination operand is a memory operand, the operand must be aligned on a 16-byte boundary or a general-protection exception (#GP) will be generated. "
https://www.felixcloutier.com/x86/movdqa:vmovdqa32:vmovdqa64
> Perhaps DPDK needs a macro (like Linux kernel) for efficient unaligned
> access.
>
> In Linux kernel it is CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
next prev parent reply other threads:[~2022-07-01 8:10 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-15 7:16 [Bug 1035] __rte_raw_cksum() crash with misaligned pointer bugzilla
2022-06-15 14:40 ` Morten Brørup
2022-06-16 5:44 ` Emil Berg
2022-06-16 6:27 ` Morten Brørup
2022-06-16 6:32 ` Emil Berg
2022-06-16 6:44 ` Morten Brørup
2022-06-16 13:58 ` Mattias Rönnblom
2022-06-16 14:36 ` Morten Brørup
2022-06-17 7:32 ` Morten Brørup
2022-06-17 8:45 ` [PATCH] net: fix checksum with unaligned buffer Morten Brørup
2022-06-17 9:06 ` Morten Brørup
2022-06-17 12:17 ` Emil Berg
2022-06-20 10:37 ` Emil Berg
2022-06-20 10:57 ` Morten Brørup
2022-06-21 7:16 ` Emil Berg
2022-06-21 8:05 ` Morten Brørup
2022-06-21 8:23 ` Bruce Richardson
2022-06-21 9:35 ` Morten Brørup
2022-06-22 6:26 ` Emil Berg
2022-06-22 9:18 ` Bruce Richardson
2022-06-22 11:26 ` Morten Brørup
2022-06-22 12:25 ` Emil Berg
2022-06-22 14:01 ` Morten Brørup
2022-06-22 14:03 ` Emil Berg
2022-06-23 5:21 ` Emil Berg
2022-06-23 7:01 ` Morten Brørup
2022-06-23 11:39 ` Emil Berg
2022-06-23 12:18 ` Morten Brørup
2022-06-22 13:44 ` [PATCH v2] " Morten Brørup
2022-06-22 13:54 ` [PATCH v3] " Morten Brørup
2022-06-23 12:39 ` [PATCH v4] " Morten Brørup
2022-06-23 12:51 ` Morten Brørup
2022-06-27 7:56 ` Emil Berg
2022-06-27 10:54 ` Morten Brørup
2022-06-27 12:28 ` Mattias Rönnblom
2022-06-27 12:46 ` Emil Berg
2022-06-27 12:50 ` Emil Berg
2022-06-27 13:22 ` Morten Brørup
2022-06-27 17:22 ` Mattias Rönnblom
2022-06-27 20:21 ` Morten Brørup
2022-06-28 6:28 ` Mattias Rönnblom
2022-06-30 16:28 ` Morten Brørup
2022-07-07 15:21 ` Stanisław Kardach
2022-07-07 18:34 ` [PATCH 1/2] app/test: add cksum performance test Mattias Rönnblom
2022-07-07 18:34 ` [PATCH 2/2] net: have checksum routines accept unaligned data Mattias Rönnblom
2022-07-07 21:44 ` Morten Brørup
2022-07-08 12:43 ` Mattias Rönnblom
2022-07-08 12:56 ` [PATCH v2 1/2] app/test: add cksum performance test Mattias Rönnblom
2022-07-08 12:56 ` [PATCH v2 2/2] net: have checksum routines accept unaligned data Mattias Rönnblom
2022-07-08 14:44 ` Ferruh Yigit
2022-07-11 9:53 ` Olivier Matz
2022-07-11 10:53 ` Mattias Rönnblom
2022-07-11 9:47 ` [PATCH v2 1/2] app/test: add cksum performance test Olivier Matz
2022-07-11 10:42 ` Mattias Rönnblom
2022-07-11 11:33 ` Olivier Matz
2022-07-11 12:11 ` [PATCH v3 " Mattias Rönnblom
2022-07-11 12:11 ` [PATCH v3 2/2] net: have checksum routines accept unaligned data Mattias Rönnblom
2022-07-11 13:25 ` Olivier Matz
2022-08-08 9:25 ` Mattias Rönnblom
2022-09-20 12:09 ` Mattias Rönnblom
2022-09-20 16:10 ` Thomas Monjalon
2022-07-11 13:20 ` [PATCH v3 1/2] app/test: add cksum performance test Olivier Matz
2022-07-08 13:02 ` [PATCH 2/2] net: have checksum routines accept unaligned data Morten Brørup
2022-07-08 13:52 ` Mattias Rönnblom
2022-07-08 14:10 ` Bruce Richardson
2022-07-08 14:30 ` Morten Brørup
2022-06-30 17:41 ` [PATCH v4] net: fix checksum with unaligned buffer Stephen Hemminger
2022-06-30 17:45 ` Stephen Hemminger
2022-07-01 4:11 ` Emil Berg [this message]
2022-07-01 16:50 ` Morten Brørup
2022-07-01 17:04 ` Stephen Hemminger
2022-07-01 20:46 ` Morten Brørup
2022-06-16 14:09 ` [Bug 1035] __rte_raw_cksum() crash with misaligned pointer Mattias Rönnblom
2022-10-10 10:40 ` bugzilla
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