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Commit 0e455d8e authored by Robin Murphy's avatar Robin Murphy Committed by Catalin Marinas
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arm64: Implement optimised IP checksum helpers 



AArch64 is capable of 128-bit memory accesses without alignment
restrictions, which makes it both possible and highly practical to slurp
up a typical 20-byte IP header in just 2 loads. Implement our own
version of ip_fast_checksum() to take advantage of that, resulting in
considerably fewer instructions and memory accesses than the generic
version. We can also get more optimal code generation for csum_fold() by
defining it a slightly different way round from the generic version, so
throw that into the mix too.

Suggested-by: default avatarLuke Starrett <luke.starrett@broadcom.com>
Acked-by: default avatarLuke Starrett <luke.starrett@broadcom.com>
Signed-off-by: default avatarRobin Murphy <robin.murphy@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 33688abb

arch/arm64/include/asm/Kbuild

+0 −1
Original line number Diff line number Diff line 
generic-y += bug.h

generic-y += bugs.h

generic-y += checksum.h

generic-y += clkdev.h

generic-y += cputime.h

generic-y += current.h

arch/arm64/include/asm/checksum.h

0 → 100644
+51 −0
Original line number Diff line number Diff line 
/*

 * Copyright (C) 2016 ARM Ltd.

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program.  If not, see <http://www.gnu.org/licenses/>.

 */

#ifndef __ASM_CHECKSUM_H

#define __ASM_CHECKSUM_H



#include <linux/types.h>



static inline __sum16 csum_fold(__wsum csum)

{

	u32 sum = (__force u32)csum;

	sum += (sum >> 16) | (sum << 16);

	return ~(__force __sum16)(sum >> 16);

}

#define csum_fold csum_fold



static inline __sum16 ip_fast_csum(const void *iph, unsigned int ihl)

{

	__uint128_t tmp;

	u64 sum;



	tmp = *(const __uint128_t *)iph;

	iph += 16;

	ihl -= 4;

	tmp += ((tmp >> 64) | (tmp << 64));

	sum = tmp >> 64;

	do {

		sum += *(const u32 *)iph;

		iph += 4;

	} while (--ihl);



	sum += ((sum >> 32) | (sum << 32));

	return csum_fold(sum >> 32);

}

#define ip_fast_csum ip_fast_csum



#include <asm-generic/checksum.h>



#endif	/* __ASM_CHECKSUM_H */