arch/x86/include/asm/pmem.h

/*
 * Copyright(c) 2015 Intel Corporation. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License 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.
 */
#ifndef __ASM_X86_PMEM_H__
#define __ASM_X86_PMEM_H__

#include <linux/uaccess.h>
#include <asm/cacheflush.h>
#include <asm/cpufeature.h>
#include <asm/special_insns.h>

#ifdef CONFIG_ARCH_HAS_PMEM_API
/**
 * arch_memcpy_to_pmem - copy data to persistent memory
 * @dst: destination buffer for the copy
 * @src: source buffer for the copy
 * @n: length of the copy in bytes
 *
 * Copy data to persistent memory media via non-temporal stores so that
 * a subsequent arch_wmb_pmem() can flush cpu and memory controller
 * write buffers to guarantee durability.
 */
static inline void arch_memcpy_to_pmem(void __pmem *dst, const void *src,
		size_t n)
{
	int unwritten;

	/*
	 * We are copying between two kernel buffers, if
	 * __copy_from_user_inatomic_nocache() returns an error (page
	 * fault) we would have already reported a general protection fault
	 * before the WARN+BUG.
	 */
	unwritten = __copy_from_user_inatomic_nocache((void __force *) dst,
			(void __user *) src, n);
	if (WARN(unwritten, "%s: fault copying %p <- %p unwritten: %d\n",
				__func__, dst, src, unwritten))
		BUG();
}

/**
 * arch_wmb_pmem - synchronize writes to persistent memory
 *
 * After a series of arch_memcpy_to_pmem() operations this drains data
 * from cpu write buffers and any platform (memory controller) buffers
 * to ensure that written data is durable on persistent memory media.
 */
static inline void arch_wmb_pmem(void)
{
	/*
	 * wmb() to 'sfence' all previous writes such that they are
	 * architecturally visible to 'pcommit'.  Note, that we've
	 * already arranged for pmem writes to avoid the cache via
	 * arch_memcpy_to_pmem().
	 */
	wmb();
	pcommit_sfence();
}

/**
 * __arch_wb_cache_pmem - write back a cache range with CLWB
 * @vaddr:	virtual start address
 * @size:	number of bytes to write back
 *
 * Write back a cache range using the CLWB (cache line write back)
 * instruction.  This function requires explicit ordering with an
 * arch_wmb_pmem() call.  This API is internal to the x86 PMEM implementation.
 */
static inline void __arch_wb_cache_pmem(void *vaddr, size_t size)
{
	u16 x86_clflush_size = boot_cpu_data.x86_clflush_size;
	unsigned long clflush_mask = x86_clflush_size - 1;
	void *vend = vaddr + size;
	void *p;

	for (p = (void *)((unsigned long)vaddr & ~clflush_mask);
	     p < vend; p += x86_clflush_size)
		clwb(p);
}

/*
 * copy_from_iter_nocache() on x86 only uses non-temporal stores for iovec
 * iterators, so for other types (bvec & kvec) we must do a cache write-back.
 */
static inline bool __iter_needs_pmem_wb(struct iov_iter *i)
{
	return iter_is_iovec(i) == false;
}

/**
 * arch_copy_from_iter_pmem - copy data from an iterator to PMEM
 * @addr:	PMEM destination address
 * @bytes:	number of bytes to copy
 * @i:		iterator with source data
 *
 * Copy data from the iterator 'i' to the PMEM buffer starting at 'addr'.
 * This function requires explicit ordering with an arch_wmb_pmem() call.
 */
static inline size_t arch_copy_from_iter_pmem(void __pmem *addr, size_t bytes,
		struct iov_iter *i)
{
	void *vaddr = (void __force *)addr;
	size_t len;

	/* TODO: skip the write-back by always using non-temporal stores */
	len = copy_from_iter_nocache(vaddr, bytes, i);

	if (__iter_needs_pmem_wb(i))
		__arch_wb_cache_pmem(vaddr, bytes);

	return len;
}

/**
 * arch_clear_pmem - zero a PMEM memory range
 * @addr:	virtual start address
 * @size:	number of bytes to zero
 *
 * Write zeros into the memory range starting at 'addr' for 'size' bytes.
 * This function requires explicit ordering with an arch_wmb_pmem() call.
 */
static inline void arch_clear_pmem(void __pmem *addr, size_t size)
{
	void *vaddr = (void __force *)addr;

	/* TODO: implement the zeroing via non-temporal writes */
	if (size == PAGE_SIZE && ((unsigned long)vaddr & ~PAGE_MASK) == 0)
		clear_page(vaddr);
	else
		memset(vaddr, 0, size);

	__arch_wb_cache_pmem(vaddr, size);
}

static inline bool __arch_has_wmb_pmem(void)
{
	/*
	 * We require that wmb() be an 'sfence', that is only guaranteed on
	 * 64-bit builds
	 */
	return static_cpu_has(X86_FEATURE_PCOMMIT);
}
#endif /* CONFIG_ARCH_HAS_PMEM_API */
#endif /* __ASM_X86_PMEM_H__ */