[v1] Optimize bpf_csum_diff() and homogenize for all archs

[PATCH bpf-next 1/5] net: checksum: move from32to16() to generic header

Posted by Puranjay Mohan 1 month ago

from32to16() is used by lib/checksum.c and also by
arch/parisc/lib/checksum.c. The next patch will use it in the
bpf_csum_diff helper.

Move from32to16() to the include/net/checksum.h as csum_from32to16() and
remove other implementations.

Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
---
 arch/parisc/lib/checksum.c | 13 ++-----------
 include/net/checksum.h     |  6 ++++++
 lib/checksum.c             | 11 +----------
 3 files changed, 9 insertions(+), 21 deletions(-)

diff --git a/arch/parisc/lib/checksum.c b/arch/parisc/lib/checksum.c
index 4818f3db84a5c..59d8c15d81bd0 100644
--- a/arch/parisc/lib/checksum.c
+++ b/arch/parisc/lib/checksum.c
@@ -25,15 +25,6 @@
 	: "=r"(_t)                      \
 	: "r"(_r), "0"(_t));
 
-static inline unsigned short from32to16(unsigned int x)
-{
-	/* 32 bits --> 16 bits + carry */
-	x = (x & 0xffff) + (x >> 16);
-	/* 16 bits + carry --> 16 bits including carry */
-	x = (x & 0xffff) + (x >> 16);
-	return (unsigned short)x;
-}
-
 static inline unsigned int do_csum(const unsigned char * buff, int len)
 {
 	int odd, count;
@@ -85,7 +76,7 @@ static inline unsigned int do_csum(const unsigned char * buff, int len)
 	}
 	if (len & 1)
 		result += le16_to_cpu(*buff);
-	result = from32to16(result);
+	result = csum_from32to16(result);
 	if (odd)
 		result = swab16(result);
 out:
@@ -102,7 +93,7 @@ __wsum csum_partial(const void *buff, int len, __wsum sum)
 {
 	unsigned int result = do_csum(buff, len);
 	addc(result, sum);
-	return (__force __wsum)from32to16(result);
+	return (__force __wsum)csum_from32to16(result);
 }
 
 EXPORT_SYMBOL(csum_partial);
diff --git a/include/net/checksum.h b/include/net/checksum.h
index 1338cb92c8e72..0d082febfead4 100644
--- a/include/net/checksum.h
+++ b/include/net/checksum.h
@@ -151,6 +151,12 @@ static inline void csum_replace(__wsum *csum, __wsum old, __wsum new)
 	*csum = csum_add(csum_sub(*csum, old), new);
 }
 
+static inline __sum16 csum_from32to16(__wsum sum)
+{
+	sum += (sum >> 16) | (sum << 16);
+	return (__force __sum16)(sum >> 16);
+}
+
 struct sk_buff;
 void inet_proto_csum_replace4(__sum16 *sum, struct sk_buff *skb,
 			      __be32 from, __be32 to, bool pseudohdr);
diff --git a/lib/checksum.c b/lib/checksum.c
index 6860d6b05a171..025ba546e1ec6 100644
--- a/lib/checksum.c
+++ b/lib/checksum.c
@@ -34,15 +34,6 @@
 #include <asm/byteorder.h>
 
 #ifndef do_csum
-static inline unsigned short from32to16(unsigned int x)
-{
-	/* add up 16-bit and 16-bit for 16+c bit */
-	x = (x & 0xffff) + (x >> 16);
-	/* add up carry.. */
-	x = (x & 0xffff) + (x >> 16);
-	return x;
-}
-
 static unsigned int do_csum(const unsigned char *buff, int len)
 {
 	int odd;
@@ -90,7 +81,7 @@ static unsigned int do_csum(const unsigned char *buff, int len)
 #else
 		result += (*buff << 8);
 #endif
-	result = from32to16(result);
+	result = csum_from32to16(result);
 	if (odd)
 		result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
 out:
-- 
2.40.1

Re: [PATCH bpf-next 1/5] net: checksum: move from32to16() to generic header

Posted by kernel test robot 1 month ago

Hi Puranjay,

kernel test robot noticed the following build warnings:

[auto build test WARNING on bpf-next/master]

url:    https://github.com/intel-lab-lkp/linux/commits/Puranjay-Mohan/net-checksum-move-from32to16-to-generic-header/20241021-202707
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
patch link:    https://lore.kernel.org/r/20241021122112.101513-2-puranjay%40kernel.org
patch subject: [PATCH bpf-next 1/5] net: checksum: move from32to16() to generic header
config: x86_64-randconfig-122-20241022 (https://download.01.org/0day-ci/archive/20241022/202410222149.3FVJFYYy-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241022/202410222149.3FVJFYYy-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202410222149.3FVJFYYy-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
>> lib/checksum.c:84:34: sparse: sparse: incorrect type in argument 1 (different base types) @@     expected restricted __wsum [usertype] sum @@     got unsigned int [assigned] result @@
   lib/checksum.c:84:34: sparse:     expected restricted __wsum [usertype] sum
   lib/checksum.c:84:34: sparse:     got unsigned int [assigned] result
>> lib/checksum.c:84:16: sparse: sparse: incorrect type in assignment (different base types) @@     expected unsigned int [assigned] result @@     got restricted __sum16 @@
   lib/checksum.c:84:16: sparse:     expected unsigned int [assigned] result
   lib/checksum.c:84:16: sparse:     got restricted __sum16

vim +84 lib/checksum.c

    35	
    36	#ifndef do_csum
    37	static unsigned int do_csum(const unsigned char *buff, int len)
    38	{
    39		int odd;
    40		unsigned int result = 0;
    41	
    42		if (len <= 0)
    43			goto out;
    44		odd = 1 & (unsigned long) buff;
    45		if (odd) {
    46	#ifdef __LITTLE_ENDIAN
    47			result += (*buff << 8);
    48	#else
    49			result = *buff;
    50	#endif
    51			len--;
    52			buff++;
    53		}
    54		if (len >= 2) {
    55			if (2 & (unsigned long) buff) {
    56				result += *(unsigned short *) buff;
    57				len -= 2;
    58				buff += 2;
    59			}
    60			if (len >= 4) {
    61				const unsigned char *end = buff + ((unsigned)len & ~3);
    62				unsigned int carry = 0;
    63				do {
    64					unsigned int w = *(unsigned int *) buff;
    65					buff += 4;
    66					result += carry;
    67					result += w;
    68					carry = (w > result);
    69				} while (buff < end);
    70				result += carry;
    71				result = (result & 0xffff) + (result >> 16);
    72			}
    73			if (len & 2) {
    74				result += *(unsigned short *) buff;
    75				buff += 2;
    76			}
    77		}
    78		if (len & 1)
    79	#ifdef __LITTLE_ENDIAN
    80			result += *buff;
    81	#else
    82			result += (*buff << 8);
    83	#endif
  > 84		result = csum_from32to16(result);
    85		if (odd)
    86			result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
    87	out:
    88		return result;
    89	}
    90	#endif
    91	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH bpf-next 1/5] net: checksum: move from32to16() to generic header

Posted by Toke Høiland-Jørgensen 1 month ago

Puranjay Mohan <puranjay@kernel.org> writes:

> from32to16() is used by lib/checksum.c and also by
> arch/parisc/lib/checksum.c. The next patch will use it in the
> bpf_csum_diff helper.
>
> Move from32to16() to the include/net/checksum.h as csum_from32to16() and
> remove other implementations.
>
> Signed-off-by: Puranjay Mohan <puranjay@kernel.org>

Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>

Re: [PATCH bpf-next 1/5] net: checksum: move from32to16() to generic header

Posted by Daniel Borkmann 1 month ago

On 10/21/24 2:21 PM, Puranjay Mohan wrote:
> from32to16() is used by lib/checksum.c and also by
> arch/parisc/lib/checksum.c. The next patch will use it in the
> bpf_csum_diff helper.
> 
> Move from32to16() to the include/net/checksum.h as csum_from32to16() and
> remove other implementations.
> 
> Signed-off-by: Puranjay Mohan <puranjay@kernel.org>

Acked-by: Daniel Borkmann <daniel@iogearbox.net>

[PATCH bpf-next 1/5] net: checksum: move from32to16() to generic header
[PATCH bpf-next 2/5] bpf: bpf_csum_diff: optimize and homogenize for all archs
[PATCH bpf-next 3/5] selftests/bpf: don't mask result of bpf_csum_diff() in test_verifier
[PATCH bpf-next 4/5] selftests/bpf: Add benchmark for bpf_csum_diff() helper
[PATCH bpf-next 5/5] selftests/bpf: Add a selftest for bpf_csum_diff()