Commit 434b2660 authored by Heiko Carstens's avatar Heiko Carstens
Browse files

s390/rwonce: add READ_ONCE_ALIGNED_128() macro 

Add an s390 specific READ_ONCE_ALIGNED_128() helper, which can be used for
fast block concurrent (atomic) 128-bit accesses.

The used lpq instruction requires 128-bit alignment. This is also the
reason why the compiler doesn't emit this instruction if __READ_ONCE() is
used for 128-bit accesses.

Link: https://lore.kernel.org/r/20230224100237.3247871-2-hca@linux.ibm.com


Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
parent ebf95e88

arch/s390/include/asm/rwonce.h

0 → 100644
+31 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 */



#ifndef __ASM_S390_RWONCE_H

#define __ASM_S390_RWONCE_H



#include <linux/compiler_types.h>



/*

 * Use READ_ONCE_ALIGNED_128() for 128-bit block concurrent (atomic) read

 * accesses. Note that x must be 128-bit aligned, otherwise a specification

 * exception is generated.

 */

#define READ_ONCE_ALIGNED_128(x)			\

({							\

	union {						\

		typeof(x) __x;				\

		__uint128_t val;			\

	} __u;						\

							\

	BUILD_BUG_ON(sizeof(x) != 16);			\

	asm volatile(					\

		"	lpq	%[val],%[_x]\n"		\

		: [val] "=d" (__u.val)			\

		: [_x] "QS" (x)				\

		: "memory");				\

	__u.__x;					\

})



#include <asm-generic/rwonce.h>



#endif	/* __ASM_S390_RWONCE_H */